I believe this should be the original payment itself, based off [this code for the offsets association](https://github.com/spree/spree/blob/a3b8476140ce2e9bb13807d99cf268901436cfe6/core/app/models/spree/payment.rb#L11-L12) and [this code for the crediting of normal payments](https://github.com/spree/spree/blob/a3b8476140ce2e9bb13807d99cf268901436cfe6/core/app/models/spree/payment/processing.rb#L100-L107).

Could you please update this?