When you reach scale as a lead generation agency, it's inevitable that you will reach out to the same lead on behalf of multiple clients.
The numbers at the end of custom variables are the "ID" number of the Campaign in Smartlead.
The structure of custom variables is
if the custom variable you select is called somethingcustom
and the id of the campaign in smartlead is 123456
Then you would use {{somethingcustom_123456}} as the variable.
This is ONLY true when using the Native Pitchlane to Smartlead integration.
We do this so that the lead can have multiple pitchlane videos in multiple campaigns and the custom variable is not overwritten.