Yes you are calculation the record ID#, but my suggestion is to make a new numeric field called [Markup Level] and make that the Key field of the markup table. The you will calculate the markup level with the 40 line IF statement.
As for this part of your question
I want to change the 10 above 11,
I did not understand that question.
Also pay attention to my other suggestion that you don't want historical pricing to be affected when you change the discount levels in your master Markup table..
When the order has been invoiced, you would then trigger a native Action to copy the values from the markup lookup value into the frozen lookup value so that it would not change if you changed your discount structure in the future. so the formula for the markup would actually be to use the frozen value if there is one, else use the lookup, and that is what would be passed down to the child records.