Sentence:  the anaconda reaches a length of at least 37 feet , the reticulate python 33 , the African rock python 25 , the amethystine python at least 22 , the Indian python <WSD>20</WSD> , and the boa constrictor 18 - 1 2 . 
Meaning of the word marked with <WSD> tags:  denoting a quantity consisting of 20 items or units