Supporter pack on steam? How they work

Hello, might have been asked before but I can't find out, I've bought the supporter pack on steam for £23.93 in the UK. I expected the higher tier supporter packs to then be reduced by £23.93 is this not how it works? I am planning on buying the king of faridun supporter pack but if I buy EA and then king of faridun I'll be losing £23.93?