老板什么意思？我要回他吗？ 回什么？

老板今天早上给我发了一个EMAIL， 说

I have been spending a lot of time with the .............. you worked on. I just wanted to thank you for all of your hard work and for doing such a good job on it.

前几天他指出好几次我哪里做得不够好， 今天发了这么个EMAIL， 什么意思啊？ 我
要回他吗? 回什么？