4 Stroke engine oil questions??

Hi.
Just a few questions regarding engine oil in modern 4 bangers. I change my engine oil every practice day (about 2 hours of riding in total for the day) and every single race/heat/qualifier on race weekends.

i had a pretty short practice session last weekend due to feeling under the weather and the weather being silly hot and humid so i only did 3 10/15 min sessions and wasn't really on the pace. i jet washed, lubed and locked in the gararge for the week. took it out today to prep it for racing tomorrow. warmed her up for 3 mins in order to drain the oil. when i took the oil filler cap off it hissed at me like there was lots of pressure and heat in there and when i put the dipper in it showed no oil in there. i emptied it and there was only about 200-250 ml of oil in the engine as opposed to the 700 that should be in there.
so i paniced and refilled with fresh oil hoping that the bike was ok. i kicked over a few times to work some oil through and she started fine.

so, where the hell has the oil gone and has this potentially caused damage.
also, it seems to me that the whole oil amount thing is more of an art than a science. i've noticed that when i put fresh oil in and then put the dipper in the oil level is right at the max amount, then once i kicked over a few times and warmed up its just a few ml's above the minimum level. so i kind of figure that it's impossible to keep an accurate measurement of how much oil is in the bike at all times. just seems a very hap hazard and innacurate way of measuring oil.

any ideas for either problems?

Thanks for your replies. appreciated.
basically i was making 1 point and asking 1 question i guess.

firstly i find the whole oil thing in four strokes a bit hopeless.
i always measure my oil exactly, both in engine and tranny. i empty the old stuff, put in some fresh stuff and and the dip says good to go. i know i've put in the correct amount anyway but i always check the dipper when i put fresh oil in cause it gives me a good starting point to measure for the rest of the day.
so, off i go racing, end of race, let it cool, check dipper. wipe it and dip. measures that there is no oil in there at all.
now the idea of the dipper is to measure very roughly if you need to top up the oil (at least that is the manuals explanation for it, it actually states that if the dip stick measures low, add more oil. well after running the bike the dipper measures no oil at all so technically i should put another 700ml of oil in but of course that would then mean i was running almost double the amount of oil that should be in there.
basically i just think the dipper is a pointless addition to four strokes and it just confuses me rather than helps me measure my oil correctly.

anyway my second concern was where the hell did 500 ml of oil dissapear to.
i put 700 in, ran it, and got 200 out.
no leaks and no performance problems.
wtf?

even if i was a complete retard, there is no possible way that i could incorrectly measure 700ml of oil.
i.e. no measuring mishaps.