I must be reading the figures wrong. I thought the "For" votes...

I must be reading the figures wrong. I thought the "For" votes plus the "Discretionary" votes (which would have been voted for} should equal the total votes "For" but in all cases the total was higher and the "against" percentage was lower in the "total votes cast". Can anyone tell me where the extra "for" votes came from? Probably a logical explanation I'm just not seeing.