Consider that each line in a conversation is a separate text. So if you have a 5 min conversation with a friend, each of you spends 15s on a reply, then you have 10 texts in that conversation. And that was just a short conversation.
If you phrase it as "the average teen says 94 sentences to his friends each day", that doesn't sound so extreme. And a good portion of those sentence will come in a few much longer conversations.
The average boy sends 2,815 text messages per month? 94 per day? 6 per waking hour, every hour, every day, every week for a month? On average?
The average girl sends 8 text messages per waking hour, every hour?
Wow.