Welcome back to JaY/Momoyukiis knows nothing about medical stuff

Ok this is nothing to do with anything and I’m asking something kinda specific here but does anyone know anything about peak flow readings or peak flow meters?

I have to use a peak flow meter for two weeks and started using it yesterday night. Yesterday night and this morning I got highest readings of 310 and 300. Just now, it’s night and the highest reading I got was 240?

I’m only meant to record the highest out of three tries each day and each night but the lowest I got just now was 190 and now I’m just confused like is that normal for it to drop so much?