Strange conversion from epub to kepub

[Sam Sahara]

Calibre 3.6
Kepub metadata writer 2.7.1

If I take an epub with the following code into the .css file:

.colophon {
  font-size: 0.92em;
  text-indent: 0;
  text-align: center;
}

and convert it in kepub I obtain a file with the following code in the .css file:

.colophon {
    display: block;
    font-size: 0.75em;
    text-align: center;
    text-indent: 0;
    margin: 0
    }

QUESTIONS:

1. Why the font-size value is changed from .92em to .75em?
2. Is it a good practice to manually re-change the font-size value into the kepub opening it with an archive manager?

Thanks.

[GeoffR]

This is normal for all Calibre conversions, it is not KePub specific. You might want to disable font size rescaling in the conversion options.

A Calibre conversion makes a lot of changes to the stylesheet properties and CSS cascade structure, so books that have been through a conversion (even just an ePub -> ePub conversion) will often display differently to the original.

Edit: If you use the KoboTouchExtended driver, it can send an ePub to the device as a KePub without going through the Calibre conversion process. This might give better results than converting ePub -> KePub in Calibre.