Current round takes more than 10 hours now.
The hashing power is calculated from current round at the pool's end. So if you have started during current round, your shares submitted during your connection are divided by the whole time that has elapsed from current round start, i.e. longer than you've been submitting. The ratio converges to the correct value as the time goes, but will never reach it. In the next round, the calculation will be OK already (as long as you won't disconnect).