Look at the tooltips on the bubble at the right side of your picture.
Tooltips are related to N. of transactions
The holding period for trades comprising multiple buy transactions (which is what the tooltips would have shown you) is an average, weighted by the number of shares.
it started on 08.07.2022
thats not 153 days until today
~$ date -d "-153 days"
Do 4. Aug 14:40:11 CEST 2022
because all transactions are counted
Seems a stupid approach to count holding period but thanks for explanation.