This is the 10551st most frequent Russian word.
включительно
"Inclusive" or "up to and including."
The word 'включительно' here indicates that both the first and the tenth days are included in the range.
Дни с первого по десятый включительно закрыты для посещения.
The days from the first to the tenth inclusive are closed for visits.
In this case, 'включительно' specifies that the mentioned range ends with the labeled chapter being part of it.
Я прочитал главы со второй по пятую включительно.
I read chapters from the second to the fifth inclusive.
Here, 'включительно' conveys that the last mentioned date is also part of the specified period.