There seems to be a difference between the available Store Credit of yours with the site currency you had picked previously. Would you like to:
Fortnite ACCOUNTS USD $6.1
Fortnite ACCOUNTS USD $10.3
Fortnite ACCOUNTS USD $11.2
Fortnite ACCOUNTS USD $9.3
Fortnite ACCOUNTS USD $2.68
Fortnite ACCOUNTS USD $5.36