Someone can explain this better than me but:

The Aluminum arrow numbers correspond to the diameter of the shaft and the wall thickness. 24 is the diameter and 15 is the wall thickness of the aluminum.

On the carbons the 60/70 of the particular arrow your looking at is supposed to be spined for a 60-70 draw weight.

There is a lot to learn and a lot to proper spine selection. I would suggest listing your spec' s on here and see what people come up with.
What kind of bow, poundage your shooting, arrow length,release,etc.