Above-average compared to other professors or compared to the general population? I haven't read anything about their findings but I'd imagine 94% being above average compared to the general population would be on the low side.
"First I am interested in why people tend to have overly favorable and objectively indefensible views of their own abilities, talents, and moral character. For example, a full 94% of college professors state that they do "above average" work, although it is statistically impossible for virtually everybody to be above average."
average of entries 0, 10 of 11 entries above average
I'll bet that the typical college prof believes that a small fraction of her "peers" rate -1000 or worse.