The "manual shift" you are using is actually just a gear limit. It limits the highest gear based on what you have selected. Otherwise the automatic shift schedule is unchanged until the highest gear allowed is reached. From the manual:
"Electronic Range Select (ERS) Operation — Eight-Speed Transmission The Electronic Range Select (ERS) shift control allows the driver to limit the highest available gear when the transmission is in DRIVE. For example, if you set the transmission gear limit to 4 (fourth gear), the transmission will not shift above fourth gear (except to prevent engine overspeed), but will shift through the lower gears normally. You can switch between DRIVE and ERS mode at any vehicle speed. When the transmission gear selector is in DRIVE, the transmission will operate automatically, shifting between all available gears. Tapping the GEAR- switch (on the steering wheel) will activate ERS mode, display the current gear in the instrument cluster, and set that gear as the top available gear. Once in ERS mode, tapping the GEAR- or GEAR+ switch will change the top available gear"