Impossible to say. Anything in between 20 and 80%? Depending on the difference in hardness between the hone and the slurry stone.
It's important to know that when slurry is present, stroking with a razor not only abrades steel from the razor, but also abrades the surface of the hone, thereby releasing more slurry. That slurry obviously comes only from the Coticule.
It's rate to release fresh garnets plays a role in the speed of the hone.
Whether the rubbing stone has much influence on the honing process remains something that needs further research. I believe it does, but I have no idea at what extent.
Best regards,
Bart.