Charge plugin redirecting to page with "1" on it
I'm the developer of Charge.

I've never directly observed that behaviour, but it sounds like it's most likely hitting a redirect failure and falling back to some base success/fail responses. 

The most likely cause of that, is that you've not specified the default success route in the Charge settings. You'll find that under Charge > Settings > General > Success URL. 

In there, you can specify the exact redirect route to push a user to after a successful transaction. 

A common format would be something like thanks/{slug}, and load up your receipt template, on a path like payments/receipt etc..

Alternatively you can supply a hidden input on the form called redirect with the url you'd want the user redirected to after the transaction completes.