It's ok to not know! Josh nailed it on this post. I've too had these experiences of having one CEO pitching or in our portfolio with an answer for everything. I was oftentimes surprised at the "all-knowingness" of some of these guys. I think I'm a pretty savvy guy but I sure don't know what even one of my portfolio companies will exactly earn or spend 3 years out. It's also highly unlikely that a CEO (or a VC) will know this. I love saying "I don't know". It gives me either time to go and figure it out or do my best to give an approximation of what the answer could be.