Every movement you make is registered in your brain. Do the same movement twice and the same neuron is activated twice.
The more you repeat the movement, the deeper you carve a tunnel for that specific action. The neuron moves faster as the tunnel gets deeper. That means, when you repeat one measure 30 times you’ll play it 30 times better.
I’m not a science buff but I wanted to share what I learned from reading The Talent Code.( If I’m not right please feel free to correct me 
.)
There is something called myelin. It’s a layer that grows on the neuron to make it faster and stronger. The more you repeat something, more layers of myelin will cover the neuron, making your performance more accurate.
Combine deep practice with smart repetitions and you’ll reach the best of you.
The book is great, get it here.