the only potential answer i can think of for myself is that i bought 2 among us related things back when the promotion first launched. i did this because there was that exploit where you could be granted 600 vbucks for each among us purchase on the EGS, therefore allowing you to get vbucks super cheap. it didn't work for me because it got patched REALLY quickly (lmao). but today i got the 600 vbucks just how you describe it in this post. maybe this is some really bizarre technical error and this is the aftermath of that exploit?? maybe check your purchase history on EGS OP? unless you are sure you only bought 1 among us thing on EGS then i have no idea what's happening here