You can't. It's a unique image identifier, so it looks like the 43nd image you opened in that Gimp session (count starts at 0).
However, if you want a different display in the titlebar, you can cheat...
The title bar contents are created from a "format string" where items identified with a %X notation are replaced by data from the image:
In this image 7.0 means it's the 8th image, 1st view (because you can create several views per image). But you can replace %p.%i by a fixed value (after all the "." between them is a fixed value, as ar some other punctuation characters) so for instance "0.0":
If you try you'll see that the image title bar is updated as you type, so if this is for a one-shot screenshot, you don't even need to set the preferences.
However, if you want a different display in the titlebar, you can cheat...
The title bar contents are created from a "format string" where items identified with a %X notation are replaced by data from the image:
In this image 7.0 means it's the 8th image, 1st view (because you can create several views per image). But you can replace %p.%i by a fixed value (after all the "." between them is a fixed value, as ar some other punctuation characters) so for instance "0.0":
If you try you'll see that the image title bar is updated as you type, so if this is for a one-shot screenshot, you don't even need to set the preferences.