The unbounded difference conjecture for unknotting and slicing genus

Let $K$ be a knot, let $u_s(K)$ denote its slicing number, and let $g_s(K)$ denote its slice genus. Unbounded difference conjecture. The difference

$$u_s(K)-g_s(K)$$

can be arbitrarily large. This predicts that slicing number can exceed slice genus by an unbounded amount; the source gives no resolution or further context for the claim.