Think back to when you first started texting on your good ol’ indestructible Nokia brick. While hammering out messages you may have noticed a counter ticking down from 160 next to a 1. When that counter hit 0, you’d see that 1 that was sitting next to the 160 jump up to a 2.
This means you’d end up with two messages on your bill. This first number was counting how many characters you had left per segment and the second one was counting how many segments you had used.
Read more about message segments from Twilo here