Apple Health Negative Daily Step Values

This article pertains to: Inform (v2)

While very rare, it is possible that you might see a daily step value in your Summary data that is a negative value for Apple Health as a source.

This generally only happens if the user has multiple different sources providing step data to Apple Health on their phone.

The step values that Validic receives from Apple Health are not the total steps from all sources but rather Apple Health’s aggregation of steps. Apple Health de-duplicates steps when there are multiple sources for a single time period. This is how they attempt to prevent duplicate counting of the same physical activity.

The intent of the Validic Mobile SDK’s integration with Apple Health is to represent the step value as shown to the user on the steps dashboard. Apple Health updates steps throughout the day as values come in across sources. The aggregation value from Apple Health is different from the total (all) steps when the user is tracking activity with more than one source. Apple Health uses the priority of sources and date/time of steps to determine which steps to use and which to ignore. Apple has their own algorithm which is not publicly documented.

But how does this result in negative steps?

Validic reports manually-entered steps and aggregate steps as provided by Apple Health. Apple Health does not provide a "device" step count.

Because of that, Validic calculates the device steps based on the difference between the manual and aggregate steps (device steps = aggregate steps - manual steps). So if Apple were to report a higher manual step count than the aggregate that would result in a negative device count.

A scenario where we have seen this happen is when 1) a user has multiple sources for steps in Apple Health AND 2) the user is manually adding more steps to a lower priority source than were captured by a higher priority at the same time.