If the currency shown on your Xiaomi phone's Themes App differs from your actual region, it depends on the region selected on your phone. The currency symbol in the Themes App aligns with your Xiaomi account's region.
If you're signed into your Xiaomi account on your phone, the Themes App uses your account's region, and the Themes content and currency are based on that region. You can check your Xiaomi account's region by going to [Settings] >> [Xiaomi Account].
If you're not signed into your Xiaomi account on the device, the system region set in Settings is used, which can be found under [Settings] >> [Additional Settings] >> [Region].