The "clip.dat" or "video.dat" file is an autogenerated file created when you run Coach Paint. This file stores and "reserves" the memory that you are willing to use in the future.
Let's see an example, if you set 100GB storage in the Config Editor, the ".dat" file would have a 100GB size, and all your Coach Paint work would be stored in there. Unfortunately, the file can not autoregulate itself, so it would be constantly consuming 100GB of storage, even if you are just working with one clip.
You can always select how much memory you want coach paint to use, by changing the "video file size" in the Video tab of the config editor:
How much memory should I configure?
If you are used to working with long or multiple clips at a time, we recommend at least 100GB of storage memory. This will allow you to confidently work with the software.
Of course, if you don't have that amount available, you can select a lower value and can increase it later, depending on your needs. A 50 GB value should be enough if you don't work with more than 10 clips at the time.
We don't recommend setting less than 20GB of space, as the software won't have the capacity to operate correctly due to the lack of space.
We also recommend reading the "How to increase VIdeo File Size?" article for a better understanding.