Howdy Fred,
I would love to help you with this. That’s definitely an issue between your theme and WooCommerce, but that does not mean there is no solution. Have you ever added any CSS to your themes files before? If so it’s just a little dash of that. Add this CSS:
.woocommerce .quantity input.qty{ width:8em; }
And you will notice the amount picker is now wide enough to actually show the numbers. Did that do what you wanted?
If you have never added CSS before you might try using Simple Custom CSS.
Does that all make sense? Will that work for you? Please let me know.
Cheers!
– Brook