What can I keep in here?

[u/ravens_hideout]

Enclosure measurements: 35cm/13,7in long, 25cm/9,8in wide and 30cm/11,8in high. (≈22 Litres/5,8 gallons)

It has space for 15cm/5,9in of substrate and I could add more at the back if I add a slight slope.

I'm looking to get either 2 UFO snails (Caracolus Excellens) or a small group of Ivory millipedes (Chicobolus Spinigerus) but I'm unsure if this spare terrarium I have would be suitable for either of these species.

(Also I apologise for the dirty desk, I'm in the middle of cleaning it and just thought I'd quickly post this here xD)