Hi, 

when selecting part linked with left side 

for drawer an slack of 1.5mm ( 20.55 diagonal measurement rounded to 20.6)

for door an slack of 3mm ( 20.72 diagonal measurement rounded to 20.7)

you can set each slack to 3mm

Other point

I can already see a difference on drawers of cabinet with the rounded dimensions.

in the menu Tools > Units you can change the precision and this has an influence on the displayed result

the 3 drawers are in an area of 700 mm height + (18 mm bottom cover – 1.5 mm slack = 16.5) + (9 mm half shelf cover – 1.5 mm slack = 7.5) – (2*3 mm between drawers = 6 mm) , 700+16.5+7.5-6= 718 divided by 3 fronts = 239.333….

The single drawer are area of 215.3 + 16.5 bottom cover + 7.5 top cover = 239,3

IF you reduce 3 drawers area zone to 699mm, and single area to 215mm that give you 7 drawers with equals height

I hope this makes sense to you

All the best, Alexandre