Total population = 100%, let's say 100 people Turnout = 70% means that 70 people went to cast votes, 30 abstained. Now, if you have 50-50 (50% vs 50% remis) means that 35 people said 'yes', 35 people said no. One more person from ones who abstained up to this point went and cast a vote for yes. Now we have: Turnout: 71%, 71 people Yes: 50.7% or 36 people out of 71 No: 49.3% or 35 people out of 71 EDIT: each time I wrote 'people' I meant it as a shorthand for 'people eligible to cast votes' for purpose of this example.
OK, I got it. Thanks! :) I misread the OP. I thought when it said counted, it meant counted as staying, not just the percentage of people counted in general. I was reading that as 51.6% as voted for staying and 51.7% as voted for leaving. But it meant 51.6% counted in total and 51.7% voted for leaving and 49.3% for staying.