I see you have multiple subscriptions. If you have multiple subscriptions, the total number of products appearing in a subscription will usually be less than the total number of products in your category. I think that accounts for the disparity. I did not see the total change for any subscription after clicking find in your store.
As for the auto-update, that's a V3 feature... meaning the products on your website will be automatically update at an interval you set. It has nothing to do with subscriptions, though subscriptions are set up to make sure your store has new products in it. That was a V1 feature and is a V3 feature.