Sort of a Necro, but...
He's doing a multiplier based on which skill a unit has. The multiplier for Knockback seems substantial, the multiplier for Slow seems negligable... at least in Monica's case.
He's also including range into the multiplier, (which is arguably irrelevant, if there's a steady enough stream of monsters such that there's always *something* in range) and speed (unclear if he's simply using the A-B-C-D-E rating and assigning a point value (which again, is pretty much completely irrelevant) or is actually using attack speeds gleaned either from other posts (such as the DPS thread) or by timing the speed himself.
Seeing as his "overall boss strength" (where all that should matter is speed and stats) is completely different than the DPS threads, (where it's actually using timing how long it takes between each attack) I expect he's just assigned a multiplier to each letter.
i.e. the table is exceedingly wrong in design.
That said, there's also something fubar in calculations, though since we don't know the multiplier values for the different skills/range/speed, hard to say for sure.
Seth has same speed, same cost, same range and same skill as Monica, mostly lower stats, yet 2 to 4 times the quest values. So yeah, something way off on the calculations too.