At what point is the fuel light supposed to come on? Mine comes on briefly when you turn the ignition on then goes out. I went out today and the gauge dipped below slightly below E but still no light. Filled her up anyhow and she took 17 litres so i'm suspecting here was more to be had but didn't fancy running out in the middle of nowhere...
As mentioned, it depends on the bike model and also if your reading is taken on a hill or on a flat as to the operation of the fuel warning light.
The 02/03 foxeye models will do about 18.4 ltrs before reserve light and you have another 3.6 litres in reserve after this. As another member mentioned, these models normal will light up when the needle gauge is halway on the "E" mark roughly.
If your light should come on in a flat road, it might go off again going up a hill as the fuel is sent back towards end of the tank where the sensor is so the level will rise, which your sensor will interpret that it has more fuel than it actually has.
The 01 models had a litre less, so it should still do 17.6 litres before the light comes on too, which would account for your light still not coming on if your fill up only took 17ltrs.
Seems to me you have one of these models and if you had driven another 10-20 miles, you would have activated the warning light and gone into reserve. It is working and the bulb ain't blown because it flashed on in a pre-check when you turned on the ignition.