Actually, now that I think about it I believe the ID of the 1617 is .216".
With the first two numbers being OD in 64th's; SO, 16/64=.25....and then the last two numbers being wall thickness in thousandth's;
SO, ID=OD-(Wall Thickness)(2) or ID={16/64(or .25)} - { (.017)(2)}(or .034)
SO, ID=(.25-.034)=.216
It looks like you(or I) used the two sets of numbers in the opposite order, which when I do that I get the .2336 that you did. Can someone please confirm which of us is right and which is wrong?