SRS = Speed Reference System. Put very simply the pitch bar on the flight director will provide guidance as to the correct attitude to fly in order to achieve and maintain target airspeed once airborne.. .. .FLEX = derated power used for take-off.. .35 = a numerical value calculated for the prevailing take off conditions e.g. wind temperature runway length etc. The higher the number the less thrust is being used for t/o.. .. .The crew on your video where reading out the active flight director mode(SRS) and autothrust mode (FLEX) from their instrument displays.