Question: If BSNL Dataone connection is activated on 10th Jan., what free usage in Jan.will be allowed ? 

Answer: you didnt tell about your plan(500 or 250) anyway ..you have only 22 days after activation so you will be having \n  (total free usage /  total no of days in the month) * \n(the days after activation)\n for example if your free usage is 1Gb for January month then \n      (1024 mb*/31)*22 = 726.7 Mb or 744150.7 Kb
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