As I do not know the details of the servo lib I cannot confirm this bug but your text seems to make sense.
I can confirm this code exists in 0.22 in Servo.cpp (not in .h) so it is indeed there for some time.
You can report this bug @ - Google Code Archive - Long-term storage for Google Code Project Hosting. -
Do you have a fix for the code please post it here too.
The "+4" on line 92 should be on the other side of the inequality, OR it should be a "-4" instead.
Should the +4 in line 95 be changed too, or is this coincidentaly the same magic number?