Yeah, the gun there at CHS appears to be 3-5 mph higher than reality. I've taken an interest in this across MLB, too, over the years. Yankee Stadium is 3 mph high. Target Field has been pretty accurate over the years. This "analysis" is pretty subjective, but it's easy to see the difference between ballparks, and you have to assume the lowest readings are the most accurate.
I don't have a lot to compare CHS to, other than Target Field, but I think it's an easy comparison. You do have to be careful to not give a lot of credence to Bailey Ober's 92-93 mph fastball at Target Field on Tuesday, as that dipped quickly to 89 once the adrenaline wore off.
So, yeah, Duran. If he's in the high 90s, that's pretty good.