The electrophoresis test is not exact. If you were to repeat the test, you would most likely see slightly different results. You probably do have a level of HbF that is not being measured in the test, and this relies somewhat on the expertise of the lab tech running the test, so small amounts can be missed. However, there is no reason to expect the percentages to be exactly as the child's as other genetic factors do play a role. Again, HbF adds the the total Hb level, so it is not a problem at all.