Geo coding data entry

when creating/modifying an Event, the Configure Event, Event Location screen allows user input for Latitude, Longitude coordinate values, however when these values are saved, the system changes them to some other values. There does not appear to be any logic, i.e. it is not that the fields are truncated values, but they are change to some other values (they seem to be in the same area, but with no particular logic, 28.06725 was changed to 28.0628801 and -82.42377 was changed to -82.4261566). It is necessary for me to input specific Geo-coordinates for some events which will be held on the USF campus which do not have specific street addresses. Therefore I must input the Geo-coordinates instead of an address. The system appear to accept the input values, however when the location map is displayed it uses the changed values which is not acceptable because it will direct attendees to the wrong location. I have tried this a number of times and it always changes the input values, but does not indicate they were in error or that they were changed.