I've never used jsRender before, but this template seems to give you the correct output. You need to iterate over the items in the R1 array using a for
loop:
<script id="template" type="text/x-jsrender">
{{for R1}}
Column: {^{:#index+1}}
{{for #data}}
<p>{{:K1}} {{:K2}}</p>
{{/for}}
<br>
{{/for}}
<br>
</script>