RFM69W Channel mechanism
Pretty much you can set whatever center frequency you want (to a precision of 61Hz) and whatever bandwidth you feel. All this is dependent on your bit rate and partially on the modulation scheme - OOK isn't spectrally efficient while 4FSK uses half the bandwidth of 2FSK for the same data rate. 

If you had say, &lt;10kHz bandwidth, then you could possibly fit 100 channels in a 1MHz span, while a 300kHz bandwidth would only get you 3 channels in the same frequency span, that's why it doesn't specifically list things like "Channel x is on frequency y" as the RFM69 doesn't have fixed channel widths. The aren't (to the best of my knowledge) any official channel designations in the unlicensed ISM bands, every application is different so most of these little radio units are built with that flexibility in mind.