Excise registration no. query

Dear All,

I am working in manufacturing unit, one unit already registered in excise that registration no. ie. ABCDE5469BXM001, but when I registered second unit in excise I got registration no. ie. ABCDE6548BEM007, both unit is manufacturing unit but second unit registration no. is not like as provide to manufacturing unit, manufacturing unit always got registration no. like BXM001, but why the provide second unit BEM007, if anyone know about this please explain.