This diary generation message occurs before processing a BOXFIT token, if there is no text overflow to start with and if the warn if no overflow in boxfit generation option is set to true (the default).
As the behavior of this token depends on the version of QuarkXPress that you are using, the present message will be issued under different circumstances, depending on the version of QuarkXPress that you are using.
Using Quark 2016 and above
Using Quark 2015 and below
When using Quark 2015 and below, this message will be generated for any box containing a BoxFit token, and that does not have text overflow initially. If you wish to have the exact same functionality, but never see this message, then use the [BOXGROW] token instead.