Everything under is information about the last Model Action (Convert, Change Script generation, Merge) that has been used on the Model. This feature was implemented in 5.3. When you open the Model Actions window in your Model with huge number of lines (Model Menu | Manage Model Actions), you will see one or more stored Actions called last Action. As you may guess, they repeat the last Model Action without you needing to configure anything again. They are primarily meant to save time.
In your case though, you might want to delete them to save space and to greatly reduce the number of lines in your .txp file. Either delete the entire section in file or just delete all last****Actions in the Model Actions window.
We now consider implementing an option to disable automatic last Actions saving in the future version of TDM.