The Junk Store threshold is currently configured to move messages to a recipient's Junk E-Mail folder when they have a Spam ...

The Junk Store threshold is currently configured to move messages to a recipient's Junk E-Mail folder when they have a Spam Confidence Level (SCL) value of {0}. The recommended value is 4. You can configure SCL thresholds by using the Set-OrganizationConfig cmdlet in the Exchange Management Shell.