In this task you will be given a list of numbers and you need to find the mean (average) of that list. The mean of a list can be found by summing every number in the list then dividing the result by the size of that list. The output should be rounded to 3 decimal places.
[-63.025, -72.225, 75.844, 50.867, -77.069, 192.143, 34.838]