Checking oil

[Dogfuzz]

Checked oil yesterday from cold and found it between full and empty--then checked handbook and it said i should have first had the engine running at normal temperature -then switched off-waited 5 minutes--then made my dip stick check. Why the latter?--it's the first car I've owned that is recommending this. Usually it's just "check from cold ensuring vehicle is level".
What is the difference in a dip stick check when cold against the Mazda handbook advice ?

[jtonline]

The viscosity decreases as it warms up and it'll also expand. The dipstick markings and level sensors will be calibrated for warm oil.

[st3v3cx-3]

You'd have thought it wouldn't be beyond the skill of the engineers at Mazda to sort out having the cold and hot full and empty markings on either side of the dipstick, so owners could check the oil level if the engine is at normal temperature after being driven or cold before being started? Like Dogfuzz, all my previous cars from various other manufacturers have needed the oil level checked when the engine is cold.

[Dogfuzz]

If I ( and others!) have been inadvertently checking oil from cold and where necessary topping up to the maximum level-would it then follow that we would have been overfilling? how much oil is actually necessary to top up from the minimum dipstick level?
Final question- does a warning light come on if the oil level is low or too high?