Extract from Systems manual:
Normally, the target speed is economy speed above the airspeed restriction altitude and 240 knots below that altitude, until deceleration for approach. VNAV will not permit descent below the airspeed restriction altitude until the airspeed is at or below the restricted value plus ten knots. The start and end of the airport speed restriction deceleration segment is shown on the map as a green open circles with no labels.
Some people are are adjusting this speed in the DES PATH page to 250 its, in which case the monitoring will be 250-260 its.. not recommend!
If the aircraft cannot decelerate it will fly level until the speed is achieved and the path will slide down.
The "structural limit" for ONE leading edge device extended is 300 its, but Boeing allow for the worse case of multiple devices and thus limit to 230 kts. The limit is not prescribed by the trailing edge devices as if the alternate system is used to extend ONLY the trailing edge devices can be retracted and in the event of a go-around you would need to be above the trailing edge device speed with the LEDs still extended.