Yes, that's right. The engine needs to get up to its normal operating temperature with the extra lubrication of a rich mixture. So you under prop it (the manual recommends the right break in prop) and run it full throttle for the first couple of tanks to burnish the piston and liner together. Adding some extra castor oil to your fuel for those first two tanks gives you some added protection against overheating and lets your run a little faster (leaner setting) to make sure you don't get too cool.