theory: it's probably like his eyes and tongues.
i'm guessing it's 3/4 each of kira's and josefumi's balls on one side and another set on the other side.
but the true question is: is it half-penis and half-penis?

Non-Jojo reader/watcher passing by, but intrigued at the question.
(1) Why would Yasuho know the answer? Did Yasuho...? uh...
(2) Wouldn't those balls interact like balls in a Newton's cradle? Ouch.

(3) Including the penis... would it be arranged like...
[left balls] [penis shaft] [right balls]??

faramond : to answer your first question:
yes.she did.

she said it was 2x2 :

ukifuneritsu:
I read 2x2 as in like a matrix:
| ball_11 ball_12 |
| ball_21 ball_22 |