I get what the instructor was saying but it not a matter of fast or slow it is more the timing of how you release the clutch as compared to the RPM of the engine. Your clutch and acceleration should be a smooth transition with out making the bike jump or stall out. It is more a feel just like in a car, and every bike is a little different. wrong clutch release is hard on a bike and it can be even harder on you, if you release to fast with high rpm you can stall or the bike can get a way from you to slow you wont get top use of the bike if you go to slow on the clutch and the rmp and speed drops then bike will slow down over going faster and the engine will have to work harder to get you back up to speed. It is almost an art it take time to get it right.