Warning error in Protected Content

URGENT! My client can't receive payments on her site http://www.theworkshopbox.com

Getting the following error:

Warning: number_format() expects parameter 1 to be double, string given in /home3/askjill/public_html/theworkshopbox.com/wp-content/plugins/protected-content/app/helper/class-ms-helper-billing.php on line 75

But when I change it the 2 to a 1 on line 75 I get this error:

Warning: number_format() expects parameter 1 to be double, string given in /home3/askjill/public_html/theworkshopbox.com/wp-content/plugins/protected-content/app/helper/class-ms-helper-billing.php on line 75

Any help would be much appreciated.