There is often more than one way to break a total down, for example total pupils may be broken down by year group and ability to speak Welsh.
Ceir yn aml fwy nag un ffordd o rannu cyfanswm, er enghraifft gellir rhannu cyfanswm y disgyblion fesul grŵp blwyddyn a’r gallu i siarad Cymraeg.