Presuming it's US Gov't charts (NACO) that you are using.
276/18 is your Decision Height in feet (QNH/MSL).
276/
18 is visibility, RVR in hundreds of feet.
200 is height above touchdown zone in feet(QFE).
(200-1/2) is for military pilots.
For more info, try the following links:
http://www.faa.gov/library/manuals/a...ying_handbook/
(Specifically Ch8, pp8-23 through 8-25)
http://www.faa.gov/library/manuals/a...ures_handbook/ Hope this helps.