The average price of your MTF holdings in Investments section includes brokerage and other charges while average price in positions do not include brokerage and other charges and hence there will be slight variation in average price between Investments and Positions.
Further, if you have squared off part of your MTF holdings at any point, average price in Positions section will be calculated by closing out your buy trades basis FIFO (First In First Out) logic and the average price shown will be the average of the remaining buy trades. This is done primarily because ‘Investment’ section is used for long term investments and ‘Positions’ section is primarily used by intraday traders. To refer to the average price of your total buys use the Investments section on next business day.