# 4.18.3. Define an Interval for Grade Aggregation (Optional)¶

When an external LMS links to problem components in a graded edX subsection, the edX system grades the answers to those problems, and then transfers the grades back to the external LMS.

• If the link is to an individual problem component on the edX system, the edX system returns the grade for each learner immediately.
• If the link is to a unit or subsection, you can configure an interval of time for the edX system to delay before returning the grades. The edX system aggregates all of the problems in the unit or subsection that the learner answers during that interval. Aggregating grades can reduce the number of notification messages that learners receive.

By default, the edX system aggregates grades for units and subsections every 15 minutes.

1. In edx/app/edxapp/lms.env.json, change the value for the following parameter.
LTI_AGGREGATE_SCORE_PASSBACK_DELAY = 15 * 60
2. Save the /lms/envs/common.py file.