Your guy has improved 10 pts in Stamina. I can't see his projections, but 10 pts isn't bad for a guy with Stamina in the lower area for a starter.
I checked my 5 starters. They improved 3, 17, 8, 13 and 9 pts from their original Stamina number.
The guy who improved 17 pts, has a Stamina of 90. He's just a workhorse.
I have two guys with Stamina #'s around your guy's. One of mine has the same rating as Jocko and another has slightly less. They were the ones who improved 3 and 8 pts.
Your guy has grown just fine.