A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
An alternative formula. Apply it in cell C2.
="Gm1200"&TEXTSPLIT(TEXTJOIN("",,REPT(SEQUENCE(3)&",",5)),,",",TRUE)&"-"&"0"&TEXTSPLIT(REPT("1,2,3,4,5,", 3),,",",TRUE)
HTH