Adding Sum Function To Query To Sum 12 Records

I'm trying to add a sum function to my query to sum the 12 records I get back in order to see if my total charges match the amounts within a different database table. Unfortunately, now when I run the query using the sum function, I am getting very large numbers back for the charge amt and I can't figure out why. Here is the query I've written:

IF OBJECT_ID('TEMPDB..#TMP1C') IS NOT NULL DROP TABLE #TMP1C
IF OBJECT_ID('TEMPDB..#TMP2C') IS NOT NULL DROP TABLE #TMP2C

select prin_sbb, sub_acct_no_sbb, res_name_sbb, ext_stat_sbb, cur_bal_sbb, VIP_FLG_SBB
INTO #TMP1C
from Vantage.dbo.SBB_BASE (NOLOCK)
where PRIN_SBB in (6000,7500)

[Code] .....

Not entirely sure what I am doing wrong, or why the numbers are coming back so high.