Front shock brackets, book wrong again?

[Joelove]

The two front shock brackets on the chassis, the centre holes should be 300mm from the base but the measurement from the base to top rail is 355mm minus 25mm for the thickness of the top rail minus 27mm for the sock bracket to centre hole = 303mm?

I know it's only 3mm but does this matter or do I need to fit a 3mm packer under the bracket?