Apocalypse Revealed #448
448. And I heard the number of them. This symbolizes their character perceived, that it was as described hereafter.
To hear means, symbolically, to perceive. A number symbolizes the character of a thing or a state (nos. 10, 348, 364). It is the character of these people's state as described hereafter because that is what is now described in the following verses, which is why it begins, "And thus I saw."
Arcana Coelestia #10313
10313. The spirits belonging to our planet declared that they did not dare to go near them because, when they did so, not only were they seized with anxiety, but also they experienced the delusion of being bound hand and foot to serpents, from which they could not be released until they moved back. Such a delusion is due to correspondence. For a person's physical senses are represented in the next life by serpents, and therefore also in the Word the level of the senses, which is the last and lowest of a person's life, is meant by 'serpents'.