The field is too small to accept the amount of data you are attempted to add - MS Access

The field is too small to accept the amount of data you are attempted to
add - MS Access

I was just handed a query to add to a macro which simply adds to a table
called exceptions based on a certain criteria; however I'm getting the
above error.
I have read the Microsoft Support entry regarding this error and it refers
to the use of the Memo datatype in one of the fields; none of the tables
used have such a field, they are either Text or Number. Here is the query:
INSERT INTO Exceptions ( [Unique Number])
SELECT qryOutgoings.[Unique Number],
FROM qryOutgoings LEFT JOIN tblExlcusions ON qryOutgoings.[PLAN CODES]
= tblExlcusions.[PLAN CODES]
WHERE (((tblExlcusions.[PLAN CODES]) Is Null));
(Note: Yes i have changed the fields and query names for security, just in
case :) )
The datatype of the Unique number in the Exceptions table is:
Text
Field Size: 50
Its datatype from the other table (gotten through a join on the
qryOutgoings) is EXACTLY the same. So what is causing the issue?
Here is a sample of some of the data in that field, including the largest
number:
515145
132132
824
772794
What could be the problem here? Also - note this is JUST MS ACCESS - there
is no SQL Server background involved.