I suspect this document relates to your grandfather's return from France.

The map and instructions show the route from Suippes to Calas. The map is most likely traced. The TCPs marked on the map are Traffic Control Points where military police would direct traffic. The G.I. Joe's Canteen locations are basically refreshment stops and the Bivouac Area is basically a campsite. Presumably these were scheduled stops. The notation of one Bivouac Area suggests the drive was expected to take two days. Nowadays this would be an easy one-day drive, but a truck convoy at this time would be very fortunate to make 25 mph so it seems prudent to plan on a two-day drive to cover the 480 miles listed in the instructions.

Why and when was this move being made?

Suippes and Calas were both locations of U.S. Army staging camps. During the fighting, these were holding areas for personnel who were awaiting assignment to units as replacements. After VE-Day, the facilities were expanded and used to process personnel for what was officially called "redeployment" and consisted of return to the United States via ship and in most cases demobilization promptly thereafter.

I suspect this move was made after VE-Day because driving from Suippes to Calas was driving away from the front and toward the port of Marseille, which was a major port of embarkation for redeployment. Also, it just makes sense that your grandfather would have preserved a souvenir of his trip home.

The staging camps in eastern France around Reims, including Suippes, were known as the City Camps because they were named after U.S. cities. (The one in Suippes was Camp Boston.) There was another set of camps in Normandy near Le Havre called Cigarette Camps because they were named after cigarette brands. The staging camps in southern France, including Calas, were collectively known as Delta Base Section. I don't think they had any system of names and as far as I know the camp near Calas was just called Calas.

Physically, the staging camps were huge tent cities holding as many as 60,000 personnel each. In some case they were built at the location of a prewar French army base but the population in late 1945 was simply gigantic and far larger than the permanent facilities. The personnel of an arriving unit would typically be assigned to a contiguous set of tents. The camps had large hospital and mess facilities to see to everyone's needs, which was necessary because the units would arrive with only personnel and their personal effects and did not bring equipment such as field kitchens that was normally used for sustainment. The camps also provided recreational facilities and outdoor theaters for USO performances, lectures, etc. Sports leagues were organized, newspapers were published, classes were taught, movies were shown, and in general an effort was made to make the stay in the staging camps as agreeable as possible. Keep in mind there was really no military work for the personnel passing through: the camp was run by its own staff and units did not have their weapons, vehicles, or equipment so could not really do any maintenance or training activities even if they wanted to.

In addition to the opportunities within the camps, personnel also generally had freedom to visit nearby cities and mingle freely with French civilians. In some case, organized tours were offered.

The staging camps were operated by units under the control of the Communications Zone, which was the rear area headquarters. In addition, substantial use was made of local civilian and enemy prisoner of war labor. The staging camps also typically had facilities for caring for displaced persons, liberated prisoners of war, and Allied personnel. (Although there was so much work to do in the Delta Base Section area that an infantry division was given temporary duty assisting with camp administration.)

Resources:

There is a map similar to your grandfather's here: https://www.historynet.com/footlocker-strip-map-100th-infantry-division.htm

This webpage tells the story of a field artillery unit's relocation from Suippes to Calas, its time at Calas, and its embarkation on a ship at the port of Marseille, but note they made the trip via train: https://robgorrell.com/the-388th-mp-bn

Short article on Camp Lucky Strike near Le Havre emphasizing return of liberated prisoners of war: https://www.nationalww2museum.org/war/articles/camp-lucky-strike

The official history of Delta Base Section can be found here: https://cgsc.contentdm.oclc.org/digital/collection/p4013coll11/id/1310

The pictures in the linked resources should give you some idea of the scale.