Personally, I would do the following:
Set the data file's Lines Per Page to 8. So each data page contains just the right amount of data for a single label.
Then, create a virtual page with a custom size that matches that of the labels to produce. Add a Data Selection object on that page with all the data from the Data Page.
Finally, back on the main - physical - page, add a nUp Printing object, set to use the Virtual Page created above. Set the number of horizontal/vertical copies to 2X8 and make sure the option to Change Data Page With Each Repeat is ticked.
This makes maintenance and formatting much easier, in my mind.
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Technical Product Manager
I don't want to achieve immortality through my work; I want to achieve immortality through not dying - Woody Allen