Vertical or Landscape Printing

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




^FDAmerican Cheese on Biscuit American Cheese on Biscuit^FS 






^FH^FDFresh Mandarin Orange With Honey Small Cup^FS