'The first resurrection,' mentioned in Revelation 20:5, 6, does not mean a first resurrection, but the essence and primary part of resurrection, which is salvation and eternal life. There is only one resurrection to life. A second does not happen, and is not mentioned anywhere in the Bible.

(References: Apocalypse Explained 6; Apocalypse Revealed 851; Revelation 20:5-6)

'Three hundred,' as in Genesis 6:15, signifies remains. In general, 'three hundred' signifies fullness, because the number comes from three and a hundred multiplied. Both 'three' and 'a hundred' signify fullness. The significance of products or sums of numbers is seen in the simple numbers that factor into them.

(References: Arcana Coelestia 5955)