Wow - that was fast - I had posted this question to the yahoo group and already have an answer - the largest space is 99, other spaces are 97 and 98. That's even on the flip card for the machine, but I hadn't deciphered the code. The 99 is next to a square and I was supposed to know that square was a space - now I do!
Here's the new, improved anniversary date roof. I had stitched a tail on the period to make a comma.