R2-D2 has three hacked Battle Droids or "klankers" working for him. One was destroyed on the landing pad in the previous installment. However, in their final stand there are three again.
After defeating some pursuing droids, Obi-Wan states, "No doubt there's more on the way." This is grammatically incorrect. "There's" is a contraction for "there is," singular, but Obi-Wan is referring to a plurality of droids, not just a singular unit. Proper grammar would be to say, "No doubt there are more on the way."