Abnormal FileRef for document library file

Hi, we found an abnormal api behavior when attempting to get file with sharepoint api
When we use sharepoint api https://ferociagroep.sharepoint.com/sites/****************/_api/Web/Lists(@lid)/Items(@iid)?@lid=guid%27****************%27&@iid=****************&$select=FileRef to get file, we found the FileRef as below:

/sites/*******************/_vti_rb/0/19386/Berekening Inlenersbeloning en salaris/Berekening salaris Rishi Djairam .docx

However, the site root is supposed to be /sites/*******************/document, instead of the _vti_rb, does anyone what is _vti_rb?
Thank you,

Best regards,

Ethan Fang