mariadb makes non explicit rounding for DECIMAL type dynamic columns

SET @aaa = COLUMN_CREATE('sum', 18802.5);

SELECT COLUMN_GET(@aaa, 'sum' AS DECIMAL);

COLUMN_GET(@aaa, 'sum' as decimal)  

------------------------------------

18803      

Expected see here 18802.5 because i not pointed here any restrictions for DECIMAL type

So why by default DECIMAL works as INT? I think this is not expected and not correct.