Re: [8500 GH/s] Slush's Pool (mining.bitcoin.cz); TX FEES + UserDiff; ASIC tested
That depends. Have you been mining uninterruptedly with both miners in the last 10 rounds, i.e., since 01:45 UTC?
To better explain, that average hashrate at the top is an average of all workers over the last 10 rounds. So if you went down for any period of time during the last 10 rounds your average will be affected.
You will see it climb back up to normal as new blocks are found. At least as long as you continue mining at the same rate...