That's because it grew over time, to 40DD

 

Dolly Parton’s Faith Was Hard to Measure

Jason G. Edwards, Christian Century

 

Meanwhile: 

 

... in 1994, she broke her silence and told Vogue magazine (January issue, page 144): "I'm 40-20-36. I used to never tell anybody my measurements, but the older I get the more proud I am."  

Cones

 Fixed it for ya.

 

Phony baloney plastic banana good time super fake Hillbilly calcium cannons

 ‘It costs a lot of money to look this cheap’: Dolly Parton’s life in quotes

 Dolly Parton’s flamboyant, fun style: ‘I’m not a fashion icon; I’m an eyesore’