Writing on head of bolts

[D1 WTF]

Does the writing on the head of japanese bolts eg the single number.  Define its tensile strength?

[Brett]

Yep - got it in one :yes

[joshrulz]

should go from 8.8 to 10.9 to 12.9 low to highest, google bolt gradings and some reference table should pop up.
 
if you using imperial bolts 3 lines is grade 5 and 5 lines is grade 8
 
correct me if im wrong