I have 0 idea what you might have in mind.
The simplest example of structured data is a CSV (comma-separated values) structure.
It would be sufficient if everyone only posted their inputs in this format:
09 Nov 2020,7R0PX-A42AV-DCLJZ,Riptide Survivor Pack DLC Retail
11 Nov 2020,G9EYQ-FCLBH-JEQBG,Zombie Pirates
14 Nov 2020,G6Z7A-6V6ZJ-Y5B5D,Zombie Pirates
21 Nov 2020,6Z5A6-DRX5I-CM4XW,Always Remember Me Deluxe Edition
26 Nov 2020,9TZIW-9D0LE-XWD8E,Speedball 2 HD
26 Nov 2020,AJXXC-RHH44-EDNEA,TRAUMA
There could be more or less columns. The delimiter could be different than a comma (it should be different). The data could even be missing (like XXX instead of dates, of whatevers instead of keys).
The key is to keep the structure consistent.
If the game has 1-2 dupes, so it is more or less ok for creating giveaways, if 10 or more - Houston, we have a problem. Not more, not less.
What if that game with 1-2 dupes has been won 10 times over the last X months, and the one with 10 dupes has been won a 1000 times over the same period? That's 10-20% dupe ratio, vs a 1% dupe ratio. I'd find the second one less problematic.
These might be edge cases, however - without the total volume numbers - I have no way of knowing.