This question is from An introduction to RL Pages 48 and 49. This question may also be related to below question, although I am not sure: Cannot see what the "notation abuse" is, mentioned by author of book
On page 48, it is mentioned that p:S * R * S * A -> [0,1] is a deterministic function:
The dynamics function $p : \mathcal{S} \times \mathcal{R} \times \mathcal{S} \times \mathcal{A} \rightarrow [0, 1]$ is an ordinary deterministic function of four arguments.
However, on page 49, in equation 3.4, there is summation over r:
$$\sum_{s' \in \mathcal{S}}\sum_{r \in \mathcal{R}} p(s',r|s,a) = 1 ,\text{for all } s \in \mathcal{S}, a \in \mathcal{A}(s)$$
My question is, does this mean, it is possible that performing an action $a$ that takes us to state $s'$, could result in multiple rewards?