Incremental stat gains

As I understand it, up to 50m stats, the gains from gym training increase each time you train. My question is, how does this increase work?
Is it a different figure for each stat based upon each stats starting value?
Does it remember where it was if you switch from one stat to another or does it reset?
Do we know the formula or figures for how this increment increases?
many thanks.

Up to the 50 million cap gains are logarithmic exponential. *Fixed... ;)

After, they become linear.

So, if you have capped all 4 stats and you are in (say) SSL you'd receive the same gain (as each stat as the same 'gym dot' multiplier ie 9). The best gym for a drug user is George with it's 7.3. There are special gyms which offer slightly better mulitpliers, assuming you've attained the correct specifications and unlocked them...

So in Frontline you'd get a 'slightly' better train with speed & strength - But you can't train any other stat whilst this gym is being used!!! And if you've opened say Elites you get the chance to train dextrity using a multiplier of 8, again, no other stat can be trained.

I've a spreadsheet which will work out which gym is available/best to train as well gym training calculator, if you look in tutorials. https://www.torn.com/forums.php#/p=threads&f=61&t=15924994&b=0&a=0

A better word might be exponential, I think.