I very rarely see a TS provider advertise being over 30.  This provider, TS Savannah, from San Francisco is in LA for the weekend and over by LAX.  On her BP ad, she says she is 28.  Well, I saw her back in 2003, so if she is 28 now, that puts her in the 17 year old age bracket when I saw her back in 2003.

Similar to cock size advertised.  Automatically Lorena Bobbet two inches off the top.  That's cut two inches off of the advertised length and you should be relatively close to the size or within an 80 percent accuracy range.

UNLESS, this just came to mind.  Maybe TS girls reference cock size in centimeters.   That might be why we often find that their estimation is overstated cuzz my handy google calculator says 1 inch is equal to 2.54 centimeters.  

For age, take the advertised age and add ten.  Then you are in the same general percentage of knowing how old they are

Interesting.  

When I started a year or so ago with an agency, she automatically shaved a couple of years off of my age.  I don't know why, I guess it's common practice.  To this day, I still mimic her, and shave off about 3 years.  Even though I'm still very young, and I probably don't need to.  *shrug*  Maybe clients prefer younger ladies.  I dunno.

Im guessing the overall demand of the hobby is younger girls. So providers, both TS and women alike advertise younger ages.  Maybe they want the medium, as in older clients that want younger girls and younger clients who want someone their age as well.  Just as there is a market for older women.  But for the most part women age gracefully and can pull it off.

It has something to do with this study done by OKCupid:

No matter how old the man, he always prefers women in their young 20s.

On the other question, use this:
To get real length, divide advertised length by 2.  Then add 2 inches to the result.

Awww, my 1" dick is really 2.5"?!?! You're so sweet!