There are 4 (well 5 really) ride heights.
1. Access
2. Motorway
3. Standard
4. High
5. Extended
3 are selectable in normal circumstances using the ride height selector switch
1. Access
2. Standard
3. High
If you then press the switch next to the ride height selector (looks like a flat tyre!!) you can then do the following:
1. Select each height individually (Access, Motorway, Standard and High)
2. Lock the ride height in Access Height (EAS MANUAL mode) to allow the vehicle to crawl under height restrictions
3. Lock the ride height in Standard to prevent it lowering to motorway at speed - this is used when towing.
Extended ride height is a software only function that if at High the vehicle detects it is grounded out - it will try and raise the vehicle an extended amount to clear the obstacle - this height is not user selectable (unless you have a janky box thingy to tell the ECU to do so!)
So you being able to select the bottom light (Access) the flat line (Standard) and the top light (High) is normal - until you press the inhibit switch next the ride height selector, then you can select all the above plu Motorway too.
Simples (squeak)!