Hashrate is a unit that represents the number of solutions per second. Because mining clients are counting solutions directly from the software and pools are calculating hashrate from the number of shares you sent to them and share difficulty, there can be a difference between what mining client reports and what pool calculates. Minerstat reports the same hashrate as reported by the mining client and that is called "reported hashrate".
With time, these two numbers should become similar, but if they don't, you might need to:
In the end, you are getting paid from the shares you submit to the pool and not from what mining client reports.