Use the DefinedSize property to determine the data capacity of a Field object.
Use the ActualSize property to return the actual length of a Field object's value. For all fields, the ActualSize property is read-only. If ADO cannot determine the length of the Field object's value, the ActualSize property returns adUnknown.
The DefinedSize and ActualSize properties have different purposes. For example, consider a Field object with a declared type of adVarChar and a DefinedSize property value of 50, containing a single character. The ActualSize property value it returns is the length in bytes of the single character.