check oil level when engine cold or hot?

[omodos]

This has got me stumped, for all the years I have driven I have checked the engine oil level in various brands of cars when the car has been idle and not moved during the day, the x5 manual says check the oil level after letting the car rest for 5 minutes after an uninterrupted journey of 10km.
I don't see how you get an accurate reading of the oil level if after the 5mins of resting the car all the oil in the engine has not seeped back down into the sump which I guess is where the dispstick lodges.

any tips would be appreciated