You would get Radiants based on what depth you started from and reached the Core. For example: If I start at Depth 18 and reach Depth 29, I would get 10 Radiants at the end. If I were to start at Depth 23, I would only get 5.
This also means if you ran from Tier 1 all the way to the Core, you would get extra radiants too.
Perhaps something like this:
1 - 7: +3 Radiants per depth
9 - 17: +2 Radiants per depth
19 - 28: +1 Radiants per depth
this would be a reat way to promote the arcade, +1.