How to fix product addon textarea

Try this in your custom css;

#order_comments {max-width:530px; max-height:62px}

Your theme, markup and textarea size may be different to mine. Please post your url for better advice.

If your theme does not have a setting where you can enter custom css, you can use a plugin like this one:
https://www.ads-software.com/plugins/simple-custom-css/

Thank you for your reply.
I want to fix this box size https://postimg.org/image/m5suyhyo7/ I add this box (text area) with Product addons plugin.
But I use now only Text addon and it works fine but if anyone can give the solution for this problem so it will be helpfull for other.

Regards