Cache Reserve pricing

Hi, just found out that I got charged 9.00$ instead of 4.50$ for Class A Operations (writes).
Could someone explain why?

Cache Reserve Storage (in GB-Month) 04/02/2023 - 05/01/2023 0.10234 $0.00 $0.03
Cache Reserve Writes 04/02/2023 - 05/01/2023 1,718 $0.00 $9.00
Cache Reserve Reads 04/02/2023 - 05/01/2023 14,975 $0.00 $0.72

maybe anyone could comment? Support is not helping, saying that is ok, but I don’t find WHY, as it should be 4.5$ for 1 000 000 operations, but not 1000 as it calculated here…