I'm assuming your question refers to the maximum number of lots that can be bought/sold in one order. A broker does not set the maximum number of lots of a particular contract you can trade in per order. The Exchange sets it. You can click here to know the maximum number of lots that you can buy or sell [as of April 2014].
For Nifty, its a maximum of 10,000 quantity which equates to 200 lots.