Varied result with DBC.TableSize & DBC.DiskSpace - forum topic by 02CSE33

I was going through TableSize and Diskspace views

Using the following queries : 

SELECT MAX(CurrentPerm),SUM(CurrentPerm)

FROM DBC.TableSize

where DatabaseName='financial';

O/P : 4,564,992.00 11,787,264.00

SELECT MAX(CurrentPerm),SUM(CurrentPerm)

FROM DBC.DiskSpace

WHERE DatabaseName = 'financial' ;

O/P : 6,035,968.00 11,787,264.00

I know that TableSize  should be used for Table Level details and Diskspace  for DB level. But ideally this should return the same result and indeed the CurrentPerm value is same.

Wanted to know the reason behind this.