Issue with unitStepSize and last tick

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.13.0/moment.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.1.4/Chart.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.3.0/Chart.js"></script>
<div>
  <canvas id="graph" width="300" height="200"></canvas>
</div>

JavaScript

unitStepSizenew Chart($('#graph'), {
  type: "line",
  data: {
    "labels": [1476371188357, 1476371189357, 1476396240000, 1476396540000, 1476396840000, 1476397140000, 1476397440000, 1476397740000, 1476398040000, 1476398340000, 1476398640000, 1476398940000, 1476399240000, 1476399540000, 1476399840000, 1476400140000, 1476400440000, 1476400740000, 1476401040000, 1476401340000, 1476401640000, 1476401940000, 1476402240000, 1476402540000, 1476402840000, 1476403140000, 1476403440000, 1476403740000, 1476404040000, 1476404340000, 1476404640000, 1476404940000, 1476405240000, 1476405540000, 1476405840000, 1476406140000, 1476406440000, 1476406740000, 1476407040000, 1476407340000, 1476407640000, 1476407940000, 1476408240000, 1476408540000, 1476408840000, 1476409140000, 1476409440000, 1476409740000, 1476410040000, 1476410340000, 1476410640000, 1476410940000, 1476411240000, 1476411540000, 1476411840000, 1476412140000, 1476412440000, 1476412740000, 1476413040000, 1476413340000, 1476413640000, 1476413940000, 1476414240000, 1476414540000, 1476414840000, 1476415140000, 1476415440000, 1476415740000, 1476416040000, 1476416340000, 1476416640000, 1476416940000, 1476417240000, 1476417540000, 1476417840000, 1476418140000, 1476418440000, 1476418740000, 1476419040000, 1476419340000, 1476419640000, 1476419940000, 1476420240000, 1476420540000, 1476420840000, 1476421140000, 1476421440000, 1476421740000, 1476422040000, 1476422340000, 1476422640000, 1476422940000, 1476423240000, 1476423540000, 1476423840000, 1476424140000, 1476424440000, 1476424740000, 1476425040000, 1476425340000, 1476425640000, 1476425940000, 1476426240000, 1476426540000, 1476426840000, 1476427140000, 1476427440000, 1476427740000, 1476428040000, 1476428340000, 1476428640000, 1476428940000, 1476429240000, 1476429540000, 1476429840000, 1476430140000, 1476430440000, 1476430740000, 1476431040000, 1476431340000, 1476431640000, 1476431940000, 1476432240000, 1476432540000, 1476432840000, 1476433140000, 1476433440000, 1476433740000,...