DJM-REC recording volume

Hi Pulse.
I am digging out this very old one as I still have issues with it. Lately I am recording vinyls again and it is a bit of annoying.

I still got my DJM-900nxs2 and connect my iPhone XR to it via an original Lightning cable. The recording volume is still around the -19 db when the DJM is showing an output of around 0 db.

The volume slider in the DJM-REC app is at +2.0 db.
I can push the volume in the app, by moving the slider more to the right but wanted to understand what would be thr correct handling to get the best results. As the App starts with the slider at 0 db, it feels a bit strange to push it that hard to get a 'normal' volume.

Any advice how to setup everything? Maybe I am missing something here.

Thanks

Sorry the original post was missed - have you set the output levels in the utility menu of the DJM?

On the DJM-900nxs2 the Digital Output is set to -5 db but it has the key symbol which is locked - right? Do I need to look at a different setting?

So the other thing you need to be aware of is that the recording level is taken from the channel level (the master level does not affect it), so be sure that the channel levels are nominal (around the first orange LED).

Pulse,
thanks for replying.
The Channel Level is between 0 and 3 db and should be fine. Interestingly if I look at rekordbox 6 and check the recording level for the Master Out it is over the top until the end of the strip with recording knob left at the middle position. To me that looks like rekordbox and DJM-Rec app using different recording levels.
I am doing a recording right now with the DJM-REC app with Channel Level at 0 db and the slider for the recording level in the app all the way to the right and the recording level is not more than -6 db on the app. 
Not sure if this is healthy to the recording that I have to push more or less all knobs to the red line to get a sufficient level in the recording.
Actually I have to work around it by normalizing all recordings with an external software to get accpetable recordings.
This is only with the DJM-REC app and it is with various iPhones and iPads. It is that way from the very first beginning when purchasing the app back in 2018.
Are you getting more higher levels with the app?