I feel sure this is a shortened form of 'dans le sens des aiguilles d'une montre'

Quite why that applies here I don't know, but perhaps it is something to do with adjusting this 'vernier' — to avoid inaccuracies caused by mechanical backlash, it is not uncommon to specify which direction something should be adjusted in; but there could be another meaning, as I see we are talking about 'retard', which could suggest a phase / rotating vector kind of situation. As ever, knowing a lot more about the overall context would help enormously!