The shank diameter is the first column and for Grade 5 UNF and 8.8 Metric tensile which are approximately equivalent. The second column is the common hex head size in mm for the shank with the third column the spanner/socket usage.
The above figures are for dry fitment as torque loading also dependent on whether the threads are dry or lubricated. Here is useful site which has a bit on on thread lubrication types and effects: http://home.jtan.com...KIAT/kiat_2.htm .
So, for example, a general purpose 1/2" AF Grade 5 bolt will have a shank of 5/16" and a dry torque setting of 18 lb-ft.