"Connect about every X" tells the client that you may be disconnected for periods up to X days, and to ensure that any work that is downloaded is completed by X days before the report deadline. This is the computation deadline. The client will also work harder to maintain enough work to fill this part of the buffer than the other part of the buffer.
"Additional work buffer" does not count as time possibly disconnected, and no attempt is made to finish work early as a result of this setting. In 7.x this is used as hysteresis instead of a fixed buffer size.
Connect every 8 , additional 0 will attempt to finish all work 8 days before the deadline, and will maintain a work buffer of 8 days.
Connect every 4, additional 4 will attempt to finish all work 4 days before the deadline, and will maintain a work buffer of 4 to 8 days.
Connect every 0, additional 8 will attempt to finish all work at the report deadline, and will maintain a work buffer of 0 to 8 days.
NOTE: if the time between request and deadline is < the total work buffer, the client will get into serious deadline trouble.