check out what this article on FG from this year says about changeup IVB
not sure if he's just wrong if they display it differently
https://blogs.fangraphs.com/the-more-it-stays-the-same-the-less-it-changeups/
"Changeups, like most other pitches, are designed to sink, so a positive IVB number means more relative drop. That -7.6 inches is relative to induced break for your average right-handed..."