(top-minus ra-stack offset)
If offset = 0, then calculate the stack location by: (height ra-stack) - 1 If offset > 0, then: (height ra-stack) - 1 - offset or equivalently: (height ra-stack) - (offset + 1)
(height ra-stack) - 1
(height ra-stack) - 1 - offset
(height ra-stack) - (offset + 1)