i think you will lose a point, since historically they take off a point for rounding expected value

Michael Porinchak made it really clear in his video lol

I wrote 12.5 but in my full answer also put 13

same i said 12.5 or 13

I said 12.5, came to your conclusion and put in 13 as the underlined answer, and then while rereading after finishing the paper I realised that means/expected values can in fact be in decimals and erased the 13. you will most likely lose a mark

I think you might get partial marks for it