@alex.hong I found this thread while doing some research on the $source values for myself too. It turns out, some of the $source value has a lookup table here in this reference below.
Has anyone also found information on what a positive number may indicate too? I have quite a few $source values listed as numbers such as 21, 113, 130, etc.
How does -50 “Shopify (subscribe)” differ from -6? Does -50 mean any time someone ‘subscribes’ via a purchase, a sign-up form, or other method? What if just have an email newsletter box at the bottom of our site, what $source would that be?