Arcana Coelestia#7685
7685. 'They were extremely severe' means that they penetrated every single part. This is clear from the explanation here above in 7684.
Arcana Coelestia#7684
7684. 'And rested at all the border of Egypt' means at the outermost parts there. This is clear from the meaning of 'the border' as what is outermost, and therefore 'rested at all the border' means that the falsity, beginning at the outermost, penetrated all parts of the natural, and came to an end in the outermost parts, as accords with what has been shown in 7645.