Why are the ranges different when I use Calculate Nash equilibrium and the Calculate buttons?

The two buttons perform different operations, so the difference in results is normal

1) Calculate Nash ranges button will find an approximate nash equilibrium solution for all players using pure strategies. Pure strategies mean that in player ranges the hand is either played or not. Mixed strategies could use a hand a % of the time different from 0 or 100.
With that said a precise Nash equilibrium with pure strategies almost never exists.

2) The Calculate button works completely different. It fixes all opponent ranges right where they are and calculates one range for hero given the situation. Since Nash equilibrium was an approximation, this precise result will almost always be somewhat different. In some special cases it can be significantly different, it would mean that situation is difficult and unstable.

We have an article where I explain this effect in more detail:

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