The AdSense Analytics Code (ASAC) is the additional snippet of code you must place in your webpage's HTML if you want to link your AdSense account to multiple properties within your Google Analytics account.
The ASAC must be placed above the AdSense ad code for your AdSense account to be properly applied to multiple properties.
An example of the AdSense Analytics Code is shown below. The account number and property index fields will be automatically populated once you link your accounts.
<script> window.google_analytics_uacct = "UA-accountnumber-propertyindex"; </script>