When printing A3 paper sizes it shows a bunch of incorrect numbers after the decimal point. A3 is defined by ISO 216 and all dimensions are rounded to the nearest millimetre, meaning that A3 is exactly 420x297mm.
When using acrobat to print (with units set to "millimetres" and using A3 paper size) it shows the paper size as 419.99 x 297.01 mm. Not only are these extra numbers useless, they are also incorrect.