The article 251 days are consecutive calendar days, so a weekend inside the period counts. Fill in the adjacent rest days only if an unjustified day falls immediately before or after them: that is what article 256(3) makes cost triple.
Article 256(3) pulled 2 of rest or public holiday into the pay-loss period, because an unjustified day fell immediately before or after them. It is why one badly placed day can cost three.
The holiday renunciation in article 257(1)(a) does not cover the whole loss: article 238(5) only allows renouncing the days exceeding 20 working days, which on a 22-day year is two days.
Beyond the pay, the unjustified days also fail to count towards seniority (article 256(1)).
All three paragraphs speak of «consecutive» days, that is calendar days: five days for a death on a Thursday run out on the following Monday.
These figures are the statutory floor and they are gross. Article 250 allows a collective agreement or the contract to grant more days, and a bereavement day is ordinary pay, so it carries income tax and the 11% social security share.