[NotMyWay]

By reading directly off the freestats,

for every (+1) STR, your damage is increased by 1 after calculating defence
for every (+5) STR, your damage is imcreased by 6 after calculating defence

if u had (+16) freestat STR, u would deal an additional 19 damage.
16/5=3 Remainder 1
3*6=18
18+1=19


the same is true for INT. Also, criticals cause u to deal twice ur damage, and i believe this would mean that u get 2 times the bonuses from STR if u get a crit. however, when ur damage gets to be really high, like say above 600, you may want to recalculate to see if SPR will provide more damage increase.