The printing fields are working properly in the latest development version. My understanding is that the Fields: Left, Right, Top and Bottom are to add extra space around the printed pattern.
It seems that the Top, Bot are not adding any length to paper. The paper length is the same even if you add 1 m extra space. The bottom value just moves pattern on the paper, but because the paper length is not extended the patter will be cut off in the before it is printed.
To test: Adjust the values and look the proposer paper length. It remains the same