How many units of lye needed depends on the size of the hair.
1 unit of lye = 0.1mA administered in 1 second. Use 1 unit of lye and release it and count seconds until your hair starts releasing that’s how much of units of lye needed. Villous hairs can take 15-20 units at 0.1mA, very corse hairs up to 80 units/seconds at 0.1mA.
Froth out of the follicle is normal and good sign. Froth from lye does not damage surrounding tissues. Damage occurs on deeper dermis layer if you use too much lye than needed.
Charts for multiple needle galvanic will have longer times because MNG machines are designed to release lower currents than single needle galvanic machines. You will find DC /units of lye chart from Michael Bono’s book.
this link has helpful info for single needle galvanic.