In classical logical usage, ẓann is a judgment whose evidence favors one side while leaving the opposite possibility open. It is not simply arbitrary suspicion or baseless guessing.
Suppose a shop usually opens at a certain hour. Available evidence may support “The shop is probably open today,” although a holiday or unexpected closure remains possible.
Certainty excludes the contrary in the relevant evidential setting; probability favors a conclusion without excluding its contrary. The rhetorical syllogism is defined in relation to the latter degree.