I would simply state "That is considered confidential information at my current employer. I would consider an offer in the ballpark of /x/." 2 Things - It sho

I would simply state "That is considered confidential information at my current employer. I would consider an offer in the ballpark of /x/." 2 Things - It shows that you take confidentiality seriously even when looking at leaving your current company (and its likely the policy there anyway). Secondly, it is truthful.