In the below label ZPL, I'm seeing some misalignment with TB and FB commands, even though both are having same y-axis specified in the Field Origin (FO). why is it so? How do I make it print from bottom margin instead of starting it from middle?
Also is there any restriction on using the FB and TB commands with FWR/FWB commands. Because with FWR/B and TB/FB commands are not aligning properly within the label. Any suggestions ?

^XA ^MMT ^PW447  ^CI28   ^LS0  ^LH0,0 ^LL812
^FO10,100
^A0B,30,30
^TBB,400,60
^FDAmerican Cheese on Biscuit American Cheese on Biscuit^FS 

^FO70,15
^GB1,700,3,B,0^FS

^FO80,100
^A0B,27,27
^FB400,3,1,L,0
^FH^FDFresh Mandarin Orange With Honey Small Cup^FS

^PQ
^XZ

regards,
Karthik