Handwritten Book Pages don't work with "Do until you have X"

[TheAtomicOption]

Using a wooden writer's table.

Current bills:
Make scroll (suspended)
Make handwritten book page (Do until you have 15)
Make handwritten book (Do 1 Times)

Colonist prioritized to write at the table makes book pages. There is a stack of 17 book pages in the storage zone next to the table, but the bill only shows 1/15. ( Is it counting stacks rather than summing items in all stacks?)