Can you tell me how to spell vertically within cells?
Numbers does not support vertical text format in cells. If you must display vertical text, you can write text in an object, such as a Shape or Text Box, rotate the object, and overlay the table cell, or position the object adjacent to the table. Another approach is to drag a block of text in graphic format to a cell and have the graphic become background fill. In any case, the text will not be accessible to other cells by cell reference in an expression or formula.
Here is a way to use a Shape or Text Box for vertical text and still have the Table Header cell accessible to cell references (expressions or formulas).
By Kharisma :
To be able to reference the value, create two header rows - one will be hidden, the other, visible.
Enter the actual values in the top header, then hide it.
Use the visible for the rotated text boxes or images, whichever you prefer.