Jeff selected 'Testicles' from the list and increased the counter to 2. He surmised that giving her testicles would increase the male hormones in her body, with all the associated changes that would bring.
Upon clicking to proceed, Jeff was presented with the options of subject awareness ('Selecting this option will decide whether the subject is aware of the transformation', read the tooltip) and subject history ('Selecting this option will change subject's mental make-up - creating history for the change').
Jeff chose to make Julie unaware with full history - she wouldn't suspect a thing, having been born like it.
He watched Julie's nude form on the screen change as two decent sized grapes formed on her crotch, hanging over her vagina.
Upon clicking Apply, a further pop-up box asked Jeff to confirm the changes, warning about the awareness setting and the possible consequences. He ok'ed the changes and sat back, smirking to himself.