Hey 
The Mhps number shown in your account is an estimate based on the number of proofs-of-work you sent in during the last few minutes. When you are lucky, this number will be higher than your actual hashing speed. When you are unlucky, the number will be lower.
I see! This makes much more sense now.
The Mhps number shown in your account is an estimate based on the number of proofs-of-work you sent in during the last few minutes. When you are lucky, this number will be higher than your actual hashing speed. When you are unlucky, the number will be lower.
Ill have to look into that USB stick guide too.