margin 10 is not the default

[JasonBarnabe]

wicked_pdf 2.8.2
wkhtmltopdf 0.12.6

Readme says

               margin:  {   top:               SIZE,                     # default 10 (mm)
                            bottom:            SIZE,
                            left:              SIZE,
                            right:             SIZE },

However, explicitly specifying a margin of 10 results in a larger margin than not specifying any margin.

File.open('margin10.pdf', 'wb') {|file| file.write(WickedPdf.new.pdf_from_string('test', margin: { top: 10, bottom: 10, left: 10, right: 10}))}

margin10.pdf

File.open('margindefault.pdf', 'wb') {|file| file.write(WickedPdf.new.pdf_from_string('test'))}

margindefault.pdf