Strictly speaking - there is no limit. But it is better to confirm such a certificate with an extract from the bank. Otherwise, illogical turns and questions can arise.

You submit documents to the official authority, before them the calculator, and the officers of the consulate should not think for you - how, when you receive a salary of 20 000 rubles, you are going to go to a country where one the ticket costs the same amount.

Provide additional information from the bank or a sponsorship letter from relatives. This is not difficult at all. The calculation for a certificate from a bank for the duration of your stay in Portugal goes something like this: 50 EUR per day + 75 EUR on the first day of your stay. This is a general rule for all Schengen countries.