Here the legal max in a serving (dispo purchased edible) is 10mg. Pretty sure that is a common max in many places.
It would be challenging to calculate the strength of your oil with only the number of ml (volume) because thc is generally measured in mg(weight). It is easy with bud because you often know approximately the strength of the strain - if you have 1g of bud that is 20%thc then you have 200mg thc (both weights). You need to know the concentration to calculate how much thc is in 5ml (concentration can vary widely). Did you make it or purchase it? If purchased it should give you a mg/ml on the package or something similar. If you made it is there residual solvent (ethanol), did you add any MCT to keep it fluid etc. All of which would skew the concentration. Assuming 650mg of thc/ml x 5 ml is accurate (3250mg total - it seems high but assuming it is accurate) and assuming you made the gummies with no wastage, if you divide 3250mg thc by 85 gummies you get ~38mg/gummy rather than 3.8mg (the weight you gave above). Given you said your gummies are 4x the strength of dispo gummies I assume your 3.8mg was just a typo (40mg would be a reasonable amount for 4 servings of dispo gummy).
In short, with the info you’ve given you would have to make some assumptions to arrive at an answer. Try one and see what it does to you - that will certainly tell you if your calcs are close 🙂