Transition altitude is set for your area
Transition Level is TA corrected for pressure - it could be FL63 - i.e. not a real FL....
the MIN useable FL is first real FL that gives a minimum of 500' difference between the itself and the TL i.e. in this instance FL70 (Not FL65)
The transition layer is the difference between the MIN useable FL and the TA and could therefore be in excess of 500', but should never be less than.
Hope this is useful (and factual)- a bit early in the morning for a day off, and taken from a long and distant military flying career