How to specify Photon region?

Question

Unity

I do everything according to the textbook, so everything works out, but a warning constantly pops up

PUN is in development mode (development build). As the 'dev region' is not empty (eu) it overrides the found best region. See PhotonServerSettings.
UnityEngine.Debug:LogWarning(Object)
Photon.Pun.PhotonNetwork:OnRegionsPinged(RegionHandler) (at Assets/Photon/PhotonUnityNetworking/Code/PhotonNetworkPart.cs:2444)
Photon.Realtime.RegionHandler:OnRegionDone(Region) (at Assets/Photon/ PhotonRealtime/Code/RegionHandler.cs:293)
Photon.Realtime.RegionPinger:RegionPingThreaded() (at

The settings on their website say eu;
In unity in the settings too

Yes, and is it a problem at all, all the same

PUN is in development mode (assembly development). Since "development area" is not empty (eu), it overrides the found best area.

Just to me, if the warning means something is wrong...