Is bo_Live5.dbo.BLT_BILLM the only table in your FROMlist which has sets of rows having the same value of MATTER_UNO/matter_name?
Are you expecting, in your output, only one row per matter_name?
For fast, accurate and documented assistance in answering your questions, please read this article.
Understanding and using APPLY, (I) and (II) Paul White
Hidden RBAR: Triangular Joins / The "Numbers" or "Tally" Table: What it is and how it replaces a loop Jeff Moden