Ground Gristle CD “Terus Code?”

So, with the preorder copy of my ground gristle cd, it came with a 6 digit code on the inside that i was told to not share or lose. With the front cover having the terus link on it i thought this was a personalized terus code or something but the code contains numbers and the terus page wont let you input numbers. does anybody know what this code actually does or what its used for? maybe its a bigger mystery for me to solve or something but i’ve been dwelling on it for around a month now. i even tried converting the numbers to their alphabetical place and that didnt work so… yeah, if anyone has any hints or note, please let me know. thank you :)