Depends how you convert with Calibre - I can produce 4em or 2em indents on blockquotes. Also took me a bit of fiddling to get h1 and h2 tags to be different sizes
With KinderPreviewer, it
shows a 4em indent on the blockquote but it's actually 2em when loaded onto the Kindle - which is what I told it to be in stylesheet so unless that's a conincidence...!