Sometimes, Shopify sales won't be included in the register closure on the day the sales arrive in Retail POS. This happens because payment hasn't been recorded yet. If you're still waiting for payment, a sale will come into Retail POS as a closed sale with a balance remaining. Since the payment hasn't been recorded, the sale isn't included in the closure. 

To resolve this, add the payment through the sale history. The sale will be included in the register closure on the day that you add a payment to the sale.

These Shopify sales will affect your payments report for that day but will be contained under their own regsiter closure. If you were to compare the payment report to your in-store register closure for the day, they won't match, since the payment report includes Shopify sales.