Hello,
For jpegs, using 100 is overkill. I usually use 90. The original jpeg was probably compressed in the 85-95 range.
I just tried converting some tiffs to jpegs at 85 (which is the default, I think) and GIMP showed no difference in the original and the new file. Also, I would think files this small are for the web and you could compress them even more.
-Max