'Twenty,' when referring to a quantity, signifies everything, or fullness, because it is ten twice. In Genesis 18:31, 'twenty', like all numbers occurring in the Word, signifies things and states. The significance of 'twenty' can be seen in its factors, namely, ten and two.

In the Word, 'Ten,' and 'tenths,' signify remains, i.e. every good and truth which the Lord puts into a person from infancy to the end of life.

'Ten twice,' 'two tenths,' and 'twenty' signify the same thing, but in a higher degree, namely, good. Good things in triplicate signify remains, namely, the good of infancy, the good of ignorance, and the good of intelligence.

(Odkazy: Arcana Coelestia 10222)

7842. 'Until the fourteenth of the month' means leading up to a holy state. This is clear from the meaning of 'the fourteenth day' as a holy state. 'Day' means a state, see above in 7831, while 'fourteen' has the same meaning as seven, and 'seven' means what is holy, see 395, 433, 716, 881, 5265, 5268. For multiple numbers have meanings similar to those of their factors, 5291, 5335, 5708. This explains why the Passover had to begin on the fourteenth day of the month, continue for seven days, and end on the twenty-first day, which too means what is holy, because that number is the product of three multiplied by seven. That was why there had to be a holy convocation on the first day of the Passover, and a holy convocation on the twenty-first day [of the month], verse 16.