Table in a spreadsheet means, combination of rows and columns.
 

• Select the cell number "A2", enter number "1", which represents first over.
• After pressing "enter" button, again select the cell "A2", look for the tiny square, at the right bottom corner of the selected cell.
• Take your mouse pointer over that tiny square, and drag it, till row number "21".
• Since we need to insert data for 20 overs and first row is used for naming the columns, we need to use 21 rows.

Make "over numbers" bold by selecting "Overs" column and press “Ctrl + B” key combination.