500 spam tests per month provided by the Basic subscription plan mean that you can create 500 tests in your account every month. One test includes sending the message to the GlockApps seed list and getting the report about the email placement and spam score will the spam filters and mailbox providers chosen by the user.
Automatic tests and tests via proxy addresses count against those 500 tests per month. Every time an automatic test works and/or every time you send the message to the proxy address, one credit is deducted from your account.
Unused credits in subscription plans don’t roll over the next month.