A question of height

[adapted.cat]

I recently bought IL2:1946 on steam, and have spent many happy hours since then playing it. However I must admit that I'm very confused by the course announcements over the radio when my flight reaches a waypoint.

For instance, I played the single mission US/P-51B/P-51B.mis with all the other aircraft removed to be sure that I wasn't hearing somebody else's instructions, and let the autopilot figure out the height, and here are some highlights:

Radio says: "Vector 090 Height 01 (350)"
Altimeter says: 1100'
Speedbar says: 330m

Radio says "Vector 330 Height 05 (1,500)"
Altimeter says: 1650'
Speedbar says: 500m

The heights I'm giving are the heights that the aircraft stabilizes at after the autopilot makes any course corrections. The trouble is, neither metres nor feet seem to bear any relation to the height instruction that comes over the radio. Different air forces all seem to have the same numbering scheme, too, which is strange.

There is no such ambiguity with the vector - it's simply the compass heading.

Am I just supposed to know the mapping between the number that comes over the radio and the height we're supposed to fly at? What is that mapping?

Thanks