Maybe the description of my approach can help with additional clarification. I always set page ranges as follows:
1. Create an entry as usual.
2. Double-click this entry.
3. Select the range start button.
4. Double-click on the first word of the desired range; important: the first word is not the entry itself, but any word in its environment (before or behind it). Now, before this word, an opening square bracket appears as a sign that the range begins here.
5. Go to the end of the range and mark a word here (by double-clicking). Automatically, behind this word, a closing square bracket appears as the end-of-range character.
6. Select the “Update” button. Now the view of the square brackets disappears, but they are still there. If you double click on the entry, they come to the fore.