Thank you for sharing a video, webmaster3. 

Currently, the system is designed to show two balances on a reminder email. One is their entire open balance and the other one is the balance of the invoice for which the reminder is for.

I understand that you only want to remind your customer of a particular invoice. I also like this idea since the sending reminders can be done per transaction, and if users want to do multiple invoices, then they can send a reminder for a batch of open invoices. For these reasons, I'm taking note of this as feedback to be considered in future updates. You can also send one from your QBO company by clicking on the Gear icon and choosing Feedback.

Right now, you can add a statement in the body of your email to disregard the Balance due and only focus on the Total of new charges.

Please don't hesitate to go back to his thread if you have other questions in mind. Take care and have a good one.