How dumb are some companies?
Imagine the scene ... you are going to put up a building and you have to decide how to label the floors. Now, the logical and sensible thing to do would be to use the method that the rest of the world does and use numbers (ignore for a moment the US / UK discrepency with 1st & ground floor).
What does this company do? It calls them "G" for Ground and "F" for First. Super. Everything works well.
Later, they build a new building with 3 floors.
Now they add "S" for "Second" (can you see where this is going yet?
Business grows and so does the site. Another building goes up higher than the last.
"T" for Third is born.
And then the next building ... oh dear, they really should have thought ahead.
"F" for Fourth is not an option (remember "F" for First?). So, we have "H" for erm, "Highest". Doh!
Finally, a shiny new office building is built and still, the madness continues.
"H" for Highest is still there even though it isn't the highest anymore and we have "P" for Penthouse.
Doh!