about a penny width is as good as needed - no closer than that on mine for sure

i know it says front right on the error logs but have you checked the left side as well yet ?
 
Nope havent checked the other side....Why would i..

well logically i know you wouldn't (same here) but have heard of 2 golfs so far that the diagnostic was reading LH errors that turned out to be RH

for an easy check - unplug the LH and run a test for codes

if it adds the code correct worry no more - just a chance it may be crossed over
 
Air gap fault is gap between ABS sensor & ring too large or too small.

You need to carry out wire tests between sensors & ABS Pump.

If wiring ok it will be down to sensor or pump.

Sensors are cheapest option first but make sure you fit correctly, also check ABS Rings for cracks or being out of shape.