@zeroGrav: dude youre best bet that i suggest would be typing out all the A to C (via B) flights which are 150nm and maybe avoid typing the C to A flights on the certificate.
I hope u have more than 50hours as A to C (via B). why i say this is cuz if DGCA officials check the C to A and find that its 90 nm they simply will say NO to it as a XCountry as thats their Rule.
So i hope your A to C (Via B) XC's are above 50 Hours.
Also if its around 95-97 nm u can still put it as 100nm as sometimes one gets vectored for ILS or has to do a full ILS approach or what not and a direct distance usually does not mean the actual distance.