pointed out that, despite my insertion on SR smart support (no reply by nobody), the calculation remains not correct also in CII 2019 SP1.
for example, if you insert 19.5, 20mm in the bolt diameter, the value used by the software is always 19.05mm corrensponding to 3/4" bolt... (the result remains not changed)

I presume that the software does not use the inserted value, but a table of standard diameters of bolts in US dimentions...