I have a conflict, my question is, "If I put a itunes gift card number into the area to see if it is redeemed, and it says already redeemed, does that mean it was redeemed on my account, or in general, it was already used by someone?"

I have 2 granddaughers saying the other received the gift card on their itunes account. ONe has her account info, the other can;t remember her info to log into her account, (she is young). I typrd the gift card number in from the card on one account and it says "already redeemed". Does this mean the itunes gift card was redeemed on that account, or could have been redeemed on any account, just in general already redeemed?