That number varies, it's a weekly rate. I've been with Celsius for a while now and I know USDC interest rates used to be 10+% not too long ago (a couple months maybe?). Also, that's just their US rate for USDC and a few other assets. BTC interest rate is 6.2% right now. Internationally, the USDC interest rate is 11.21% with rewards in CEL.

Celsius is a British company and is also HQ'd in the US now.