Tier 2 General - Conditions of Stay

Hi, can someone shed a light on this?

In my visa, I am only allowed a maximum of 20 hours per week supplementary work. Does this rule apply during my annual leave?
For those who are on student visas, I believe that if they are on holiday they can work as much hours as they can. However, this condition isn't exactly explained in detail in the UKBA policy guidance for Tier 2.

I worked 4 12-hour shift back in December 2014 and NHSP (Bank) only paid me for 20 hours. In technical sense, I only worked 4 12-hour shifts on that week as I was on annual leave. How stupid can this rule be? This is really frustrating because I only did those 2 shifts as a favor to my unit which was very short during Christmas week, then I ended up not being paid up until now.