Difference Between retail mark up and cost mark up

Hi,

What is the diff b/w retail mark up and cost mark in maintain primary zone group.

When i set up primary zone group for a merchandise hierarchy (Dept) with cost mark up 50%.

an Item was created in RMS in same   merchandise hierarchy(Dept) with unit ELC 100 then it's price was set in zones with 50% mark up and suggested retail was 150.

When i set up primary zone group for a merchandise hierarchy (Dept) with retail mark up 50%.

an Item was created in RMS in same   merchandise hierarchy(Dept) with unit ELC 100 then it's price was set in zones with 500% mark up and suggested retail was 1500.