No. 7 (officers of grade I, II, III)
I think there were four classes of Govt. employees before the introduction of Grade system, e,g Officer of Grade 17 and above were grouped in Class I and employees from grade 1-5 were used to be called as class IV employees. So the poster is probably asking about employees of class I, II, III and IV. (this terminology is still used by some employees although this system no more exist now)
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