Until website will have a full blown support for “checkins”, that data will not go trough when using pin# import and your only option is to use import registered competitors into the PractiScore app using CSV file.
The above link does have details for checkins (verified for Android). The most match templates have “RO” checkin defined, you can check that and define your own checkins (and even assign some colors to them in the app).
Then in your match registration form on PractiScore web site create separate checkbox fields named exactly the same as checkins you have for ROs (or else create a multiple-checkbox or radio button field named “Checkin” and add checkin names for individual checkboxes).
Then once your registration is complete you can export CSV from the shooter approval page on web site (you can open it in Excel or Google Sheets to see that the table columns are there and they match ones listed in the above link). After that send that file to one of your tablets and import it in the app from the “Import/Export” screen using “Import Registration” option in the app.
That should be about it.