So OK... I think I understand why this happen.

Probably that my standby database was stopped. The primary was running and made some switch logfiles...

I then created the standby controlfile, copied it to the standby db and started the standby db in recovery mode.

The standby db had to download the logfiles from the primary, but theses logfiles were already recorded in the controlfile because they have been created by the primary before the standby control file creation.

That's why theses logs were in double, one non applied (because the record is from the primary) and one applied (the record created by the standby.

To solve the problem :
- alter database switch logfile
- wait until the log is applied on the standby then immediately stop the standby db.
- create the standby controlfile
- replace the controlfiles on the standby db by the new standby control file.

Bye