selectpdf prints whatever it sees right there and then on the page. There are two ways in my opinion to manipulate this.
Set a delay. Some RG’s take very long to load so I always use the max delay I think its 30 secs.
When you still need to do selections, the best way to make sure it shows what you need is use url parameters that you then use to control the state of a group on the page.
For example, you have a filter on the page, a repeating group and a print button. The user makes a change to the rg based on a filter, at that point you can add a custom state to the page or the rg and when the user clicks the print button you navigate to the same page but add additional parameters to the page based on the rg’s state.
When the page loads it can set the state of the RG based on the url parameters.