odd echo when printing

so, I'm printing this:
http://www.thingiverse.com/thing:47019

when every once and a while I'm noticing the printer interface registers:

"Echo: Unknown Command:  "N58727 S1.95*56""    (or some similar numerical code at the end)

I sliced it with pronterface/skeinforge,  and i'm printing it with pronterface/skeinforge...
why is the slicer generating code the related printer soft doesn't recognize?