Benchmark in the sense what is a common baseline to compare with, e.g. most people use the yearly average S&P500 returns, or maybe the ytd return. Some people are happy when they beat the SPX even if they are still in the red.

Rate of return will vary greatly depending on your trade style and account size. I don't know what the benchmark is, but I personally consider 1% monthly growth to be very manageable with short options, not including any other income like dividends and interest on currency positions.