Raymarine i50 depth lighting

[Draughty]

I bought a new i50 depth recently. It is a standalone installation, transducer direct to instrument, power via A06049 cable I bought with it.
The manual says there are 9 lighting levels but I only see 3, none of which is ideal. RM say they would expect to see the 9 levels if the instrument was in a Seatalk ng network, it's "native habitat"! but don't seem to want to answer further.

I don't need an N2K network at the moment, when my Navman 3100s log gives up I will need one to hook up a new N2K log, my Simrad is20 wind and this i50 depth. From what I can work out I should probably do that with Micro C rather than Seatalk ng, so would this help the i50?
Any ideas out there?

Thanks