Any suggestions for arch widening with six month smile? (photos)

From your photos, it appears to me that Invisalign would be a far better choice for you. With Invisalign, you have far better control over individual tooth movement

Perhaps your dentist gave you that number as a per tooth number. The enamel is quite thick on the sides of teeth so don't be alarmed. Since your mouth is basically done growing, I think any orthodontic system would involve some inter proximal reduction(IPR). Hang in there.