The Seated ticket system always delivers you tickets that are next to each other.
Some venues number their seats only odd or even numbers, so it may appear from the seat numbers that your tickets are not next to each other.
For example, you could request 3 seats and get Row A seats 11, 13, and 15. While the numbers are not next to each other, your seats will be.
Some GA tickets may also have seat numbers assigned to them for internal box office purposes.
Don't worry! You'll be able to sit (or sometimes stand) wherever you like in the GA section.
Even if the ticket numbers in your order are not together, your group can enjoy the show together.