Here is a transcription of the handwritten portion, which refers to the message above it. Left page:

This shows a message as we receive them to make our write-ups from and lets you know what some of the letters numbers and words mean   here goes. - The NAA #2 means it was the second message sent from the Washington DC radio station that day. Z RAFT V ANON P GR 16 is the heading. The portion after the Z is who the message is sent to for action and the part after the V is the originator. In this case acting Sec. of the Navy originated the message and was sent to all naval ships and stations. The -P- designates its precedence which happens to be priority and only gives us 10 min. to be delivered to …

Right page:

[GR 16 is the number of groups.]
... an officer after we receive it off the air. In the body of the message 3401 means two things. The 34 tells what officer sent or released the message and 01 is the date. The 0340 is the time sent. Just below the message is 0045TA8470/1 Sept. 0045 is time of receipt here in our offices. TA is the radiomans initials that copied the message. 8470 means frequency he was tuned in at and 1 sept is the date. The other scratches just show we received the message and it is all taken care of. Quite a bit of work in each write up but its interesting and isn’t hard after getting used to it. - Note that time this dispatch was sent is 0340 and we received it at 0045. Difference in time belts [aka zones] is the reason.

It appears that your great-uncle was a radioman, and he sent a copy of two significant telegrams (referring to the German invasion of Poland and the Japanese attack on Pearl Harbor) along with an explanation of what all the weird symbols mean. Interesting stuff.