Update docs/src/model_simulation/simulation_structure_interfacing.md

Co-authored-by: Sam Isaacson <[email protected]>

Author: TorkelE

docs/src/model_simulation/simulation_structure_interfacing.md

@@ -183,4 +183,4 @@ oprob[two_state_model.X1 + two_state_model.X2]
 This can be used to form symbolic expressions using model quantities when a model has been created using the DSL (as an alternative to @unpack). Alternatively, [creating an observable](@ref dsl_advanced_options_observables), and then interface using its `Symbol` representation, is also possible.
 
 !!! warn
-    With interfacing with a simulating structure using symbolic variables stored in a `ReactionSystem` model, ensure that the model is complete.
+    When accessing a simulation structure using symbolic variables from a `ReactionSystem` model, such as `rn.A` for `rn` a `ReactionSystem` and `A` a species within it, ensure that the model is complete.