no worrys i had the same thought also when i first got the bike. it does not work a great deal as on a car. the best way is to drain it properly and the fill up with the amount indicated on the crank case.
Next time if your drain a heck more then check your oil pump seal, you might have 2T in the gearbox. if its less then oil leak... but you will see it on the floor most porbably when you leave the bike over night.
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feel the wind