Trying the available Display Themes, the page refreshes automatically. When you have decided, click Save to finalize the changes.
This option is useful mainly for International Users which want to bypass US Social Security Number (SSN) validation (11 characters, digits or dash).
If you check this option (and press Save), you can insert up to 30 characters. Only digits (0-9), dash, period, letters and space are permitted.
See the help page: Currency