If you are using powerstore the red question mark is probably just because some of the code is in a plugin and not on the page itself, so it can be ignored.
I'm not sure how much more detail I can give in explaining how to do it... just find where the number is referenced and wrap it with the number_format function.
So if the code was: <?php echo($number); ?>
it becomes: <?php echo(number_format($number,2,',','.')); ?>
If you want us to do it for you, or show you how in a screen sharing session, then we could do that in a premier support ticket.