Just played a 3 game series against a 4/68 at SS. in 3 games, my team only had 3 gbX to the SS. isn't that very low? also only one of those was an error, the other 2 outs. at 4/68, what dice roll even gets you an out?
Say 6000 rolls on defense in a season, 111 in a series. 111*7/216=3.6 gb(x)ss. e68 means 35% of those grounders turn into errors. So overall in a series against a ss-4e68 you can expect 3.6 gb(x)ss to turn into 1.3 errors.
An even easier way would be just 68/54 - the number of errors an e68 commits over a full season divided by the number of series in a season. 1.26 errors per series using that method.