Multifocal kidney cancer

It sounds like your surgeon is confident he can get both lesions out with minimal kidney loss, which is excellent news. The size of your lesions is indeed small...has the surgeon indicated if they are both definitely cancerous or perhaps he suspects one of them is benign? Kidney cysts are very common and many people can have several in/on one kidney. These are usually Bosniak I or II. If your scans have shown Bosniak III or IV, yes I think that is less common but by removing them when so small, a partial gives the best chance of minimal kidney loss. 

Are you likely to have a robotic? From what I've read about this (I had that), it's much more precise than any other method. They seem to prefer to do a partial wherever possible - my own surgeon told me that the chances of having to remove all my kidney, having decided on a partial, were close to just 1%. So it sounds like your surgeon has a plan and this will give you the best possible outcome.