This is humourous commentary. The competition going on is very suspenseful, and when some people are anxious, upset, or worked up and in suspense, they may bite or chew their fingernails.
The suspense is such that the commentator is suggesting, he/she is biting his nails.
Give me your fingers, Ange. I'm down to my knuckles!"
This is the humourous part. It implies that the commentator is so worked up with suspense, she has bitten and chewed away not only her nails, but her actual fingers right down to her knuckles. So she asks Ange for her fingers, so that she will still have fingernails to bite whilst the suspenseful competition continues.
Student or Learner