If the rake was 4 chips at a table of 5 I believe that would be 2 Krill. Not a 100% certain though.

Here is there info from their site:

√(rake) multiplied by (5 / players dealt) then multiplied by any other bonus factor currently in effect and finally rounded down to the nearest tenth of a Krill.

Rake at ring game tables is 1 chip per 40 (2.5% rounded down) with a cap of the lesser of 3BB or 5 chips (0.005BTC).

Limit tables with a big blind of 0.5 chips (0.0005BTC) or higher have rake of 1 chip per 50 (2% rounded down) with a cap of the lesser of 2BB or 4 chips (0.004BTC).

HU tables with a big blind of 0.5 chips (0.0005BTC) or higher have rake of 1 chip per 75 (~1.33% rounded down) with a cap of the lesser of 1BB or 3 chips (0.003BTC).

If a game would have a rake cap of 0.5 chip (0.0005BTC) then the rake cap will be 0.5 chips (0.0005BTC).