I find my attention drawn to the apparent 3% of UKIP supporters who would vote remain. It seems a little incongruous when the single biggest issue and main aim of the party is exit the EU for someone to be a supporter and not also want that outcome.
UKIP picks up the "none of the others" vote as well; some people vote UKIP to express their disgust with Labour, the Conservative and the Lib Dems. There's also a decent number of people who are Euroskeptic in that they want to see change or reform but don't want a full on leave.
Also, never under-estimate people's ability to press the wrong button.