Schau mal in die Hilfe unter "Type Compatibility". Da heißt es bei mir unter "Assignment Compatibility" unter anderem:
Zitat:
[...] An expression of type T2 can be assigned to a variable of type T1 if the value of the expression falls in the range of T1 and at least one of the following conditions is satisfied.
[...]
T1 and T2 are compatible ordinal types.
T1 and T2 are both real types.