Any ideas why container process runs as Resilio Sync user?

I am running a mysql server inside a docker container but the mysql process seems to be running under the Resilio Sync username even though it is no longer installed on my system. Is this a bug? I really do not understand why it would be running under such username.

Mysql inside your container run with an uid.
This uid is shown as the user rlsync outside the container because the same uid exist outside.

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