Partial Write beyond retention policy dropped


I am writing because of a strange problem I have with service subscriber.
I have 2 instances of influxdb OSS in 2 different virtual machine.
The first one has in input an High rate of data coming from an external program; while the second one is a replica of the first one. The replica is obtained through a Subscription.
First one has 7d of retention policy with 1h as shard duration;
Second one has 2d as RP and 1h as shard duration. I am able to see with chronograph the flux in real time in both database, but it seems some data are dropped because out policy.

I have also tryed to play with subscriber options, increasing the Writers for example, but nothing is happend.

Any ideas about that?

Thanks in Advance