Hi @ladygeekgeek
There are a few this missing with your above code:
1. You need to echo the str_replace returned value
2. Please use get_field
instead of the_field
when returning data to a function
3. Please use the $find and $replace parameters in the str_replace function.
Your code should look more like this:
<?php echo str_replace(' ', '', get_field('box_office', 'option')); ?>
Thanks
E