Flights Climbed - inaccurate, calibration how?

With and iPhone SE and Apple Watch 4; the flights climbed in inaccurate. Live in a high rise condo; so I know I will climb multiple floors but will only get 'credit' for 1 flight. Also does it matter if the iPhone is with me? Many times just have watch on.

Reviewing older posts - Apple Watch 3 and higher have barometric sensor | Know my iPhone SE does NOT have barometric sensor. Seems to be more accurate when I don't have iPhone with me.

Thanks for your time in answering my question.