The real length really varies depending on the year. When the 2363 first came out (this includes my '94, for example), the length was 23'3". This model has increased its length over the years in order to allow for a bigger bed and more space to walk around the bed. The 2363 for '07 is up to 24'4".
The same type of "rule" applies to the 1950. The 1950 (the newest floorplan, not the mid-'80's one) started at 19'11" at the beginning in 1994.5, but for '07 it's up to 20'6".
What year is the Sunline that your relative owns? Depending on the year, it may not be a 2363. Sunline had a grouping of similar models in the 22' and 24' range back in the '80's and early '90's. The 22' range is the T-2260-2263, with a length of 22'7". The 24' range is the T-2460-2466, with a length of 24'2". The 2263 and 2463 are probably the closest to the actual 2363 floorplan.
If you can walk us through where specific things are in the trailer, I can probably help you determine what model he/she has.
Irt your length question, all lengths are measured from the back bumper to the tip of the front tongue. This can change some if you have a spare tire or some other apparatus attached to the bumper, but this technically isn't part of the length.
As a general rule, the model number is the approximate length, give or take a few inches. For the most part, add about 12" to the models in the past 5-7 years.
2007 T-286SR Cherry/Granola, #6236, original owner, current mileage: 9467.8 (as of 5/26/19)
1997 T-2653 Blue Denim, #5471
1979 12 1/2' MC, Beige & Avocado, #4639
Past Sunlines: '97 T-2653 #5089, '94 T-2251, '86 T-1550, '94 T-2363, '98 T-270SR