Question regarding page numbering

[MangaD]

"Guia de Preparação da Dissertação" says the following regarding page numbering:

número de página: em numeração arábica em baixo centrado ou à direita;

But it says nothing about where the counter starts. In this template the numbering is roman for the first pages and then the counter resets at the first chapter, why?

Also, I get the following warning several times when compiling:

pdfTeX warning (ext4): destination with the same identifier (name{page.}) has been already used, duplicate ignored

Thank you for your time and attention!