Okay, so I actually heard back pretty quickly:

So 255 bars is the max of what you can set in the program, but the maximum linear amount of bars you can have including repeats and choruses is 2000. To that end, what you can set Band-in-a-Box to depends on the math. The program cannot do 40 choruses of 255 because it far exceeds that 2000 limit. You could, however, do 40 choruses of 50 bars because this would equal 2000. The program when you enter 255 bars is putting in that limit of 7 because 7 choruses of 255 = 1785 bars. Setting it to 8 choruses of 255 would push it over 2000 by about 40 measures.

We hope this helps!

Cheers,
Ember