Gift cards can be purchased in any of the specified denominations. There is no limit.
Want to purchase a higher value, simply add multiple gift cards to you cart until you reach the value you want. If ordering multiple gift cards you will be sent multiple gift card codes.
These codes can either be kept and redeemed at a later time or if you have an online account you can load the gift card balance in to that account so you do not have to keep track of the code.