A sudden increase in storage sent bytes metrics

[gause]

Hello,

I suddenly encountered a rapid increase in sent bytes metrics of my google cloud storage. 

I am using metrics to count sent bytes for each bucket per month. These metrics have the following setup:

Was there some change in counting sent bytes for buckets, that could cause this rapid increase? Or I am counting these sent bytes wrong?

My bill stayed the same for April as for March, so there is no increase in payments, event if the metrics were right it should correspond to a higher value.