Job Designation is very accurate and probably very useful. It is much more reliable than Profession.
We key in the same designation as advertised.
Sometimes some designations advertised can be done by anybody. For example - Insect Collector, this can be done just by anybody so we instead select Assistant and those else who can do this work in the salary range.
In the same way position advertised for Steno can have another designation Typist.
There is also similarity between Profession and the Job Designation but we try to be accurate with the Job Designation and ignore Profession sometimes.
So select those designations which apply to you!