Measuring DC offset.

Out of curiosity, I checked the DC offset on my solid state amp. With my digital multi-meter, the left channel fluctuated between minus 8.5mv to minus 10.5mv. The right channel fluctuated between positive 3.5mv to positive 6.5mv.

Both the inputs from the preamp and the output to the speakers were disconnected.  The amp had been warmed up for 15 minutes.   What do those results mean?