this rate --it can be more rates in fact ---is a percentage increase added to the base salary by multiplying its amount with a subunitary coefficient corresponding to each supplement. So if you'll have X as base salary, for instance X*v would be a supplement rewarding you for your previous overall time of employment(experience) or in the field , X*k is for your position, X*d-if you perform a dangerous job, X*n-for overtime work during te month,X*s-- if you perform a very stressful job and so on. At least in the public sector this is the way how the use the "coefficients",but the base varies and the calculation is a bit more complicate. I Hope it will help.