Can anyone tell me what the numbers in this circled window are used for?
Those numbers should be the car number within the train consist. Note that car numbers may not be in order and may not be consecutive. Where Is My Room On Amtrak’s Auto Train? gives examples for the Auto Train. (The Auto Train platforms have signs showing which car will be where on the platform; I've not seen that on any other train.)
The train attendants I've spoken to come up with their own rationalizations for the car numbers, but have ultimately admitted they don't know of a rhyme or reason for the car numbers being what they are.