I ran the command
EXEC sp_msforeachdb @command1="use ? exec sp_spaceused"
which returned all the relevant information per database on a SQL Server instance I was troubleshooting.
On the basis of the information I adjusted one of the db sizes .
I then ran the same command and notices that the information was not refreshing .
Adding "@updateusage = N'TRUE'" derived the latest information , and reflected the changes I made.
EXEC sp_msforeachdb @command1="use ? exec sp_spaceused @updateusage = N'TRUE';"
Source:Jack Vamvas (http://www.sqlserver-dba.com)