From the "Regulations and Instructions, For the Pursers of His Majesty's Ships and Vessels" The Purser would be required handle the Accounts and Stores of the Ship, this is a civilian position mind and had a shocking amount of latitude when dealing with their appointed duties but I digress, The Purser would ensure the ship carried all of its stores, p - Either purchasing from Private Chandlers when away from Naval Stores, or dealing with the Victualling Board at home, they accomplished this by having to lodge a bond, as well as obtain sufficient credit to purchase stores (and they would be personally liable if stores were lost or unaccounted for)... In Short, the Navy Board installed a Shopkeeper aboard the ship, and charged him with Making sure the Ship had the non-military goods to perform its duties. The Purser was beholden to the Victualling Board who would, providing that the accounts squared up per their regulations and other mandates, make good the expenses.

So having covered the the acquisition of stores for a ship, lets look at the Biscuit itself, which is quite simply a particularly large Unleavened (no rising agent) bit bread baked until hard (No moisture = doesn't go off), more reminiscent of a cracker. The Victualling board itself baked some, while other came in via Contracted Bakeries. But the End result would be the Same: 4 or 5 Biscuits would weigh about 1 pound, which is the standard ration for a Sailor per day, and they would come in a Hundredweight bag.

The Victualling Board Operated yards employed just over 4000 people, of who half would be barrel makers. The Bakers however would work 5 men to a brick oven: Forming, Baking, and then extracting finished biscuits. The only number I've seen reported speaks to 70 Biscuits a minute while the ovens were at full capacity. Any Shortfalls that the The Victualling Yards had could be made up by the aforementioned Private Companies who could fill a contract.

I highly Recommend "Feeding Nelson's Navy" if you want to look deeper into this subject.