It is important to note that the switch labelled "Altitude Hold" on the flight director panel only affects the flight director bars. With this switch in the up position (ON) the flight director bars will provide guidance for level flight. 

With the ALT PRESELECT CTRL option selected on the EFB/tablet, the autopilot will automatically capture an altitude if an altitude is set on the Altitude Preselect Controller and AUTO mode is engaged.  

With the ALT PRESELECT CTRL option disabled on the EFB/tablet, the aircraft will be fitted with a basic Altitude Alerting System which has no automatic altitude acquisition functionality. The altitude set on this panel will only alert the pilots when approaching the selected altitude, or when deviating from the selected altitude. It is up to the pilot's skill to smoothly level off the aircraft at the selected altitude and manually engaging HT (Height) mode on the mode selector panel.