First option (In/not in): Select or exclude users matching the other options selected. For the "Not in" option, AcyMailing users that are not in Community Builder will be selected, as they are thus not in the selected plan
Second option: Select the subscription plan / donation / merchandise
Third option: You can refine the filter by selecting only users that have a valid/expired/invalid subscription to the plan you selected
Fourth option: You can also refine the selected users list by filtering the user's choice on auto-recurring payment
Subscription date: It is the date when the user subscribed to the plan, not necessary the date when the subscription has been validated/paid
End date: This is the expiration date for the user's subscription. Be careful if you setup a reminder with this filter, to not send it to auto-recurring users
If your CB users are not in AcyMailing, they won't be selected. You can import your Joomla users in AcyMailing using the import page and activate the user synchronisation in the configuration.