In your sightly html of the component add the below attribute in your component div tag
Am setitng default value as 10. "perpage" is the property you set in dialog
<div class="mycomponent" data-sly-attribute.data-perpage="${ properties.perpage ? properties.perpage : '10' }">
</div>
In your java script , you can read this simple jquery selector
<script>
var perpage = $(".mycomponent").attr("perpage");
//Make a XHR call with perpage value
</script>