Differences in Holdem Resources Calculator and GTO Charts

[RangeReader]

Has anyone tried to use Holdem Resources Calculator (HRC) to try and replicate the GTO ranges presented to us in the tools section? I tried to see if HRC would give me around the same ranges that Jonathan gives us for at least UTG at 15bb but they are different. HRC recommends this range at 15bbs at a 12.5% ante UTG for a min-raise: 66+, A7s+, KTs+, QJs, ATo+, KJo+ (12.8% of hands). The GTO ranges that Jonathan gives us under these stipulations are as follows: 66+, A4s+, K7s+, Q9s+, J9s+, T8s+, 98s, ATo+, KJo+ (16.7% of hands).
Can anyone think of a reason for why this might be? Is raising these many more hands just more of an exploit rather than pure GTO?
Thanks!

[kkep]

Did you run that 9 handed or 10 handed?

[RangeReader]

Nine-handed

[PokerShaman]

I had thought that the ranges in the Tools section were made by a solver, presumably Monkersolver. HRC is nowhere near as elaborate as a solver, and so I would guess that it cuts corners in its methods to compute its ranges.

[RealJPB]

This is the answer. HRC’s main method of computing ranges appears to be being a nit.