That doesn't look bad to me. it's only 0.78% HW errors.
HW/[HW+DiffA+DiffR+DiffS]*100
17096/[17096+2132320+17200+35344]*100=0.776399208
Sigh - the issues of vendors screwing up cgminer ...
The API summary includes the (correctly) calculated HW% and also the (correctly) calculated Reject%
Pity they didn't put them on the screen there ... I wonder why?
... and just an FYI - the Reject% of the Ant is the highest of all my hardware ...