If you add a bit more txt, like 24.bde, it will display the txt below the flag correctly.
1) I would not use Nato symbols for HQs/Level His units. Thus I enter -1 in the Nato field. However, HQ units then display the Short Name on top of the National flag and it is a bit messy. Some HQ units get a zero/0 in the Nato list although you are not permitted to enter zero. But these units display properly...
Edit: Not all Nato=0 HQs display correctly, so that theory didn't hold.
In the screenshot below the British superior HQ and the French/Polish ones are displayed properly.
The British brigade HQs are not.
