The "Roll up Total ARR on Account Across all Product Instances" is a roll-up summary field that calculates the total Annual Recurring Revenue (ARR) across all product instances associated with a specific Account in Salesforce.

This field enables you to gain a comprehensive view of the total revenue generated from all active subscriptions or recurring contracts associated with the Account. It automatically aggregates the ARR values from related child records (product instances) and displays the cumulative ARR amount on the parent Account record.

By utilizing this roll-up summary field, you can easily track and analyze the total revenue impact of all product instances tied to an Account, providing valuable insights for decision-making, forecasting, and customer management.