oil level sensor accuracy?

[wba116i]

this is my first BMW so please bear with me. i have a 2007 116i - Last week while driving back from another city 'low engine oil' sign popped up and it suggested to add 1L oil. I freaked out and stopped my car to check for any visible leakages (didn't find any). And the very next day in the morning before leaving for work - i checked the oil level and it said oil level OK (right in the middle of the gauge on the dashboard). I decided to take the public transport - being unsure of the oil level readings. The reason i freaked out was because i had a oil change 6 months ago (have driven 2k km since) - when i bought the car it had 166k on the meter and now its 168k.

So, i added 500ml oil yesterday and drove for about 10km and checked the level which showed 'FULL' (image 1). and at the end of journey (50km) - the oil dropped to 80-85%(image 2).

Whats happening here? I am freaking out. Should i be worried?

[Olgeezer1]

I hate not having a dipstick. That said, you're probably fine. Your most accurate reading will be your last one, after driving 50km. You won't get any reading or anything accurate until the oil is warmed up. I always check at the end of a drive, idling on level ground.