You see - that is the way
mine some time and calm yourself
then you can experiment other combinations of the 2 values and increase the MH
for more precise settings you can read
https://raw.githubusercontent.com/ckolivas/cgminer/v3.7.2/SCRYPT-README

See You find your -g 3
may be other value of -I will give You increase
it must not obligatory to be higher than -I 18 - -I 17 may increase
experiments must be made

Have a good luck