How to know the exact open price or open tick price of crude oil mcx

for example todays open price in mkt watch is 3190 and one min chart it is 3186 in odin tick chart it is 3172 if you multiply nymex september contract price 47.06 with usdinr price at 10:00 which is 67.1675 it is 3162 …so which should be taken into consideration and it happens most of the days in crude oil and very few days it matchs like mkt watch price / i min chart price / odin tick chart price …most of the days it shows different prices i wld like to know why it happens and which price we have to take into consideration as open tick price or do we have any other way to find out please answer me appreciated in advance