To create a custom metric to track the sum of your "Donation" event values in Statsig, follow these steps:
1. Navigate to Metrics from the left-hand navigation panel, then to the Metrics Catalog tab. Click on the Create button.
2. In the Metric Type, select "Aggregation". This type allows you to compute the Sum or Average of the value or metadata property of an event type.
3. For the Event Type, select "Donation".
4. For the ID Type, select "userID" or "stableID" depending on your use case.
5. For the Aggregation Type, select "Sum".
6. For the Field, select "value". This will sum up the values you logged with your "Donation" events.
7. You can also add filters if you want to limit this metric to specific conditions, such as a certain currency.
8. Finally, give your metric a name and save it.
Please note that after you create a custom metric, it will not populate until the next day and will not backfill to previous days. Statsig will only calculate it moving forward from the creation date.