No idea but I'd love to know because I have 2 in the works accounts with spreadsheets with some hilarious margins where the data COULD be perfect but I don't know. Drives me nuts. Anyways. I don't recommend it unless you like hating yourself. As far as floors- depending on the formula I was "below" it till about 23, but some formulas are job specific. I sort of outgrew it pretty fast though.
Hi it was I who put together the chart. I just copied and pasted this chart from any other source I could find and worked with others with the numbers didn't match. I think thief may have been one of those classes, so do correct me if I'm wrong! I think the way the floors work is this: you don't have enough MP to APR out of (APR-) if you don't have enough a) HP/MP points AND b) the APR- would take you to below the floor (1800mp in this case). If you just ended up at under 1800 MP due to poor INT gear or bad job advancement rolls or whatever reason, the floor doesn't really prevent you from being there just naturally.