coolant level

[cavx5]

today i checked the coolant level on cold engine and the little plunger rises slightly above the level of the opening...earlier this year bmw replaced water pump due to what they said was a leak because i was getting low coolant level message...i checked level after the change and the plunger came all the way indicating full...now plunger is just slightly above opening..is this normal or is it still losing coolant...i have no leaks and temp gauge is normal...even before change i had no leak tech said it was leaking on to engine block before leaking to ground...2005 4.4 with 18k miles..any opinions are appreciated..thanks rob