2 things to troubleshoot.

1. Does your setup so far include relic weapons?

2.
a. Does the calculator also include atk up accessories?
b. How do accessory atk boosts work in this case? The wiki says 3-4% depending, but makes no mention of what type it is. May be additional to assault (sooo small difference), to elemental (ok difference? Not if you already Rudra), to special attack (now that's a multiplier), or maybe even its own accessory frame multiplier. This might make a huge change depending.

Edit: Ok didn't note that last part, but contributes to assault. Assume 6 atk ups from accessories, or 9 if you wanna run perfectly I guess. That's an additional theoretical 24-36% on your assault grid.