Using Gift Cards To Buy Gems... I'm Confused...

So recently I went out to my local Walmart and purchased some gift cards for my friends birthday. We both play Smite, and as I don't have a credit card, I decided to enter the code and get him some gems. The $25 gift card I had only transacted to 987 gems and only charges $18.50 and I have to forfeit the other remaining money. Is there a reason why I'm only allowed to get 987 gems, when there is obviously an option for 1500 gems that cost the same amount? I'm actually really pissed about this and I feel ripped off. I mean I did do it, having read the terms and conditions, so I can't be too mad at them, rather more at myself. Is this just something Smite does to make more money? I feel so cheaped out, sigh.

That should not be the case. What gift card did you buy? And what platform do you play on?
Was it a STEAM / PSN / XBOX gift card, or a gift card specifically for the game itself?

If it was a gift card for the game itself, something probably went wrong and you should contact Hi-Rez about it immediately. If you have any visual proof of the incident, such as a screenshot or transaction log, that will help your case a lot.

If it was a STEAM / PSN / XBOX gift card, check if the remaining money isn't stored in the person's wallet of the corresponding platform. If this is the case then something went wrong with the transaction, and only a part of the money was taken, and the rest refunded. If this isn't the case, contact Hi-Rez support and, if necessary, the support team of the corresponding platform. Once again, visual proof will help your case here a lot.

Definitely something wrong there.

If you head to your account and check out transactions, you'll see it there. If it doesn't match what you bought, you will have to contact either the store you bought it from or HiRez

I used a GameStop giftcard. I don't know if that changes anything, also I did it on a mobile device.

View your transactions through the account you used the gift card on. Check if the transaction went through correctly. Additionally, contact Hi-Rez support and, if necessary, the GameStop store you bought the card from, they should be able to help you further.

Thanks a lot I appreciate your responses