Proper way to adjust speed of transaxles?

I have an 60 inch exmark xseries (2015). The left wheel spins faster than the right at full speed (or with the levers pushed forward fully) by about 1 mph if I had to guess...it has been like this from day one (so have most other ztr's I have owned for that matter, it always seems like one side is slower than the other)

Any tips on adjusting the slow side to match the fast side would be great.
I guess my main hold up is I'm not sure if it's simply a linkage adjustment or if there is...

Proper way to adjust speed of transaxles?