User blog comment:Hayashi H/Advanced Equipment Guide/@comment-76.218.105.96-20151030035225/@comment-26486243-20151031190415

Basically what Tennousu said. The Luck formula being used to compute the ones in the above table is SQRT(70*Luck) for Torpedo and Mixed Cut-Ins, while the one used for Main Gun Cut-Ins is SQRT(50*Luck). Luck caps are assumed to be 50 for Gun, 60 for Torpedo and 70 for Mixed based on the most recent data source on the topic.

The main Combat page has not yet been updated with this new information as the bulk of the Wikia community has not yet accepted this revision to the formula, though since this affects the viability of my builds directly I've updated my own ones in advance.

If not confident in the data source, you might want to continue using the old assumptions of 40-50-60 for now, as Maruyus are difficult to get, and there is no shortage of ships that need them. Should the new formula turn out to be correct, you can always add the Maruyus to them later on.