It can be C 20/25 instead of 25/20/S (in Arabic ج 25/20), a typo caused due to copy pasting from Arabic to English document, I really do not have the clue for the same, or it can be a concrete grade name from the Arabic standard specification.
But if its like European, it means concrete with strength fck = 20 Mpa for cylinder and 25 Mpa for cube.