Tis will be fixed in 3.7.18 to the effect so you can use 'px' or '%' and if you don't use either, it will default to 'px'.
For example if you have
PHP Code:
width_1=25px&width_2=40
they will both use 'px'. if you have
PHP Code:
width_1=25&width_2=40%
width_1 will be 25px and width_2 will be 40%
note: if there are only 2 cells, then cell 2 will be the width of the page - 25px (width 1)
note: if there are 3 cells, then cell 2 will be the 40% of width of the page - 25px (width 1)
there will be some added documentation on screen for this too.