I recently used Endurance *Silk* - see my recent posting about
brushstrokes.

A 2.5L tin did two coats of around 12 to 15m^2, with some to spare.
This was on to heavish textured lining paper. I diluted it about 5%
with water for the first brush coat, and then further added about 5%
of 'Floatol' paint conditioner for the second rolled coat. Since I was
trying to get rid of brushstrokes I was a bit more generous on the
second coat than I usually am. The Floatol did seem to make the paint
'go' further.

So I'd say the estimates aren't too far out. But watch out for the
brushstrokes.

HTH
J^n