Questione giuridica chiave
Whether the cantonal court arbitrarily calculated the father's income by adding net profit, private withdrawals, and unrelated expenses.
Decisione estratta
The cantonal method was incorrect because net profit and private withdrawals are alternative and exclusive bases; adding them double-counted income.
Motivazione estratta
For an independent, income is net profit or, if accounts are unreliable, private withdrawals as an indicator of lifestyle. The cantonal court could not combine both and also mix different reference periods.