the month of February has 28 days, one week has 7 days, so any day of the week can only occur 28/7 = 4 times on that month, so the chances of getting a Wednesday, namely the favorable outcomes is 4, 4 Wednesdays on the 28 days month.
now, the Wednesdays can be on any date along those 28 days, so the 28 days will be the sample space