In reply to Paul Hy:
Aye, I can't figure out any other way they'd get the .75 from except by adding to (rather than reading down from) one of the kid sizes. Don't think any manufacturers bother with 1/4s and 3/4s except in the very low ranges.
Take 'em back, make a fuss, and point out how far wrong they were (very). Someone at that shop shouldn't be touching bindings.
In the meantime just imagine all the fun moments you could have had with your skis randomly ejecting. Even 7 is probably a bit conservative as your height comes before your weight on the chart.