I cant tell u the exact correlation of what the Dana 44 means in terms of inches or cm the ring and pinion is. I can tell u that the smaller the number (i.e. a Dana 30) will be smaller in diameter than a larger one (i.e. Dana 60). Where this comes into play the most is gear ratio at the differential.
If u are running a ratio of say 3.something the teeth will be less in number and thicker which grants you more strength. A ratio of 5.38 will make the teeth "taller" or thinner which will be compromising their strength.
When the ring is larger or bigger number, it allows more surface area for a ratio such as 5.38 to be placed on and giving them more strength by allowing them to be thicker.
Hope this helps in some way, and isn't too confusing.