the deduction shall be made from the gross salary and not in the basic salary only.. since you were away for 8 calendar days that's why their calculation is 7,300 x (30-8)/30 or 7,300 x 22/30 = 5,353.33.. do you think your company will not deduct a portion from your allowances? let say you were on leave or absent the whole month (30 days), you mean to say they will only deduct your basic salary (5,500) and the allowances (1,800) will be given to you? think about it...
of course not! you will not receive even a single penny (unless it is leave with pay).
on the other hand, the gratuity or end of service award is calculated against the basic salary..that is no. of years x basic daily rate x 21 days per year... basic daily rate is 5,500 x 12/365 = 180.82..meaning to say if you say.. 1 yr gratuity = 1 yr x 21 days /year x 180.82 = 3,797.26..or for 2 yrs = 7,594.52...