Hey @AIIA 
Any chance you replied to the wrong proposal?
Anyway, you can bridge all your BTC for the usual 0.5+% fee: https://app.rosen.tech/
For example, here the explorer page about rsBTC on Cardano: Cardano Explorer | Cexplorer.io
Side Note: if you notice the first address on that page holds 21M BTC (full BTC supply), that’s standard practice in Rosen: they mint all the possible bridgeable capital for an asset and then they break the minting key (similar concept as Single Use Seal in CKB), so that all next bridging operations are normal transfers (safer).