No you have to add a second text item to this Stack Group and after changing the function to just show ":minutes", adjusting font and size you will end up with the left picture. Now you have to change the Stacking to "Horizontal" to make a useful clock.

As you can see the size of the "wrong stacked"Stack Group has enlarged the size of the Overlap Group and so the first Stack Group with just the cards is now changed, too. This would also happen if you would have picked a font size bigger than 70.

Long story short: If you use my organized structure you can't make the font size as big as you like, because it would crash the Stack Group. Text items in Kustom have always interior margins and right now you can't adjust them.

If you want to make the text item bigger you will have to just put the items over each other without using this group structure. By this you will loose a lot of easy editing when creating KLWP presets.