Imagine your pubic bone (behind your pubic hair). Now think of your bubs head sinking into the pelvic inlet, the front of which is your pubic bone. Now divide bubs head into fifths, so just the top is 1/5th, half way to the ears is 2/5ths, at the ears is 3/5ths, etc. At 5/5ths the baby's head is so low in the pelvis it cannot be felt from outside anymore. In most mums this happens during labour.

2/5ths above brim means bubs is 3/5ths in your pelvis. That's pretty low - you're good to go. My DD's head was still 3/5ths above brim when i went into labour

Bx