I don't know personally but I just googled a few places and most say allow 1/4 border around an 8x10. Here is what one site said:
8x10" Picture Frame
Outside Frame Dimensions: 8 7/8" wide x 10 7/8" high
Viewable Picture Area: 7 1/4" wide x 9 3/8" high
allow for a 1/4" border around your 8" x 10" graphic)
I don't know if this helps, but it does look like a 1/4 maybe standard on an 8x10".