How often does it sync data from the server?

[CrazyVito11]

I just set up the app on my tablet and phone, and configured them to use my self-hosted instance of the sync server.
I then tried doing some reading on my phone, manually syncing that to the server and then checked my tablet to see if it showed up there.

Sadly it didn't show up there after waiting for 2 hours, so I did a manual sync on my tablet and that ended up writing the data from my tablet to the server instead of it downloading it.

So my question is, how often does it sync data from the server?
And is syncing manually like some kind of "force sync" that just overwrites the data on the server?

I tried looking at the source code of the app, but I sadly wasn't able to find answers there like some kind of syncing interval.
Though keep in mind that I'm not used to developing for Android, so I could also just have missed it.