Kenmore 253.6419440 top-freezer refrigerator has a capacity of 20.6 cu. ft. For marketing purposes, it would be sold as a 21 cu ft model.
I couldn't find a model 253.6449440. Is the model number hard to read? A difference of just on digit in the first four numbers after the prefix (253.) will lead to info for a different size model. The third digit after a 253. prefix indicates the second digit of the model cu ft capacity.
As an example, there is a Kenmore 253.6482440A, which is a 17.something model that would be rounded up to 18 cu ft.
If the model is a 17.X cu ft, then the refrigerator is approximately 13 cu ft and the freezer will be 3.8 cu ft.
If the model is a 20.X cu ft, the refrigerator is approximately 15 cu ft and the freezer is 5.3 cu ft.
How did you determine that the total capacity is 17 cu ft? I hope this helps!
You can find new Kenmore top-freezer refrigerators here: sears.com/appliances-refrigerators-top-freezer-refrigerators/b-1020313?Brand=Kenmore&filterList=Brand&searsTab=true