unusual behaviour of ng-checked / checkbox

<input class="ML1" type="checkbox"  ng-checked="item.ph_comp_change"  ng-model="item.ph_comp_change"  ng-true-value="1" ng-false-value="0" />

This makes an input checkbox, but the problem is I need to uncheck it 2 times, in order to remove check sign from it. But if I remove ng-true-value="1" ng-false-value="0" , it works fine.

working jsfiddle http://ift.tt/1DaTsTN

Please help me out here