Amount Error

This is an error that I received from Firstdata… It came as a result of a user entered contribution/donation amount. Would it be possible to add logic to validate a user entered amount to assure that it is a proper number as expected by firstdata? As always, Thank you for your work!

Subject: Error in form submission

This is a notification that a request for payment failed for the online store XXXXX.
An error page was displayed to the customer.

Reply to this message or e-mail Payeezy.gateway.support@firstdata.com if you have any questions.

The following errors were found:

* x_amount : can only contain digits, a comma and a decimal point.
* x_recurring_billing_amount : Invalid x_recurring_billing_amount

The parameters of the request are

‘x_amount’ : -32

https://wordpress.org/plugins/wp-payeezy-pay/