sir i'm filled 151 colleges in 2nd mock allotment but I'm not locking colleges sir so same 151 colleges are 1st round councelling in disply

Generally a candidate should fill as many choices possible.  And 150 is a good number if you have entered the choices keeping in mind you rank and category.

If you don't lock your choices, if the choice filling and locking period ends, the system will automatically lock the last saved choices. So, to be on the safer side it is advisable to lock the choices in the order of priority.

Also, the mock seats you are offered based on choice you have entered is not final. Because many candidates will change their choices based on the mock seat allotment, which will impact the final seat allotment.