How would I do the following auto-calculation?

[MNBlockHead]

I'm entering a "Class Special" that the character can use the number of times equal to their Wisdom modifier (a minimum of once).

I set the "Charge Calc Attribute" to Wisdom.

But for "Automatic Calculations", I don't know what to select.

Say character has Wisdom mod of +3

I select minimum 1. But do not know what else to select.

1+Attribute Mod. would equal four charges, where I would want 3.

I don't know why there isn't a 0+Attribute mod or just Attribute mod.