Something like below. I don't have test data, so haven't tested it yet.

Edit: The WHERE conditions on your original query caused the LEFT JOIN to become a de factor INNER JOIN, which threw off the totals. I did more of a query re-write than that to perhaps improve the query overall.

SELECT

B.SYNCHMESSAGE as 'td', '',

MAX(B.row_count) AS [COUNT],

A.IMPORTMESSAGE as 'td', '',

MAX(A.row_count) AS [COUNT]

FROM (

SELECT

, SYNCHMESSAGE, COUNT(*) AS row_count

FROM DataDEV.dbo.SYNCHTERMS

WHERE

DATEADDED >= DATEADD(DAY, DATEDIFF(DAY, 0, GETDATE()), 0) AND

DATEADDED < DATEADD(DAY, DATEDIFF(DAY, 0, GETDATE()) + 1, 0)

GROUP BY

, SYNCHMESSAGE

) AS B

LEFT OUTER JOIN (

SELECT

, IMPORTMESSAGE, COUNT(*) AS row_count

FROM Data.dbo.Data_Errors

WHERE

IMPORTDATE >= DATEADD(DAY, DATEDIFF(DAY, 0, GETDATE()), 0) AND

IMPORTDATE < DATEADD(DAY, DATEDIFF(DAY, 0, GETDATE()) + 1, 0)

GROUP BY

, IMPORTMESSAGE

) AS A ON

A. = B.

GROUP BY

B.SYNCHMESSAGE, A.IMPORTMESSAGE

ORDER BY

B.SYNCHMESSAGE DESC