The answer really depends on an assessment of each individual tooth and it’s age (as enamel naturally wears in between teeth as we age) and the relative amount of enamel available in each one (as some teeth have more enamel thickness than others) but 0.6mm is generally considered at the top end of the amount considered to be safe. Reduction of 0.5mm and 0.3mm is fairly common, however this is usually the total amount between the teeth and not on each tooth. Have you discussed other options to achieve space, including choosing an alternative orthodontic system?

If you think you’d like a second opinion than please seek one out, ideally from a specialist orthodontist or someone that can advise you from a wealth of experience, not only on Invisalign, but also on alternative orthodontic appliances

I would be more than happy to advise you further following a consultation

I hope my answers were helpful

best wishes

Mark