Hello,
Thank you for using my plugin,
TF Numbers is a custom post type, meaning you can use any “duplicate post plugin” to clone numbers set.
Number field accepts only integers, NaN is an javascript error meaning non integer value is passed to the function and it happens if you enter any symbol or letter that is not number. If you are looking to implement comma separator for numbers, you can check my controller addon – https://themeflection.com/plug/controller-addon/
Regarding adding currencies like $ (with option to show it before, or after number) you can use my currencies addon – https://themeflection.com/plug/currencies-addon/
Best Regards,
Aleksej