Ethermine - Current Hashrate constantly above and below Reported Hashrate

I am using Phoenix Miner and using Ethermine for my pool.

There is a graph at the top that displays lines for the following:

Reported Hashrate: Green
Current Hashrate: Blue
Average Hashrate: Orange

The Reported Hashrate (Green) is a straight line all the way across the chart which is great since my rig is showing 256/7mhs in the Phoenix Miner command line.

I haven't tried using any pool besides Ethermine up until this point so I am wondering if it is normal for the Current Hashrate (which I am assuming is the actual hashrate as far as the pool is concerned) to fluctuate as much as it does I have seen some crazy results overtime.

The description for Effective Current Hashrate on the Ethermine site says: "It is calculated according to your submitted shares using a 60 minute window.".

For example:

The reported hashrate line is a steady 257.

I have seen the Current hash rate anywhere as high as 320 and as low as 220 at times. Is this something to be concerned about or is it normal pool behavior? If someone could provide some insight that would be great. Thanks!