Thanks to Allen Wyatt.
Excel includes a handy time-saving feature called AutoComplete. This feature can save you time when you are entering lots of similar information in a column. You may already have noticed this feature before—when you start to type something in a cell, Excel tries to guess what you are typing and shows a “match” that you can accept simply by pressing Enter.
The “matches” that Excel uses in its “guess” is nothing but the contents of the cells in the column, above where you are making your entry. For instance, if you have information in cells A1 through A6 and you are entering a value in cell A7, Excel looks at what you are typing. If the first few characters uniquely match something in any of the six cells previously entered in the column, then Excel offers to AutoComplete A7 with the contents of the cell that matched.
Excel only tries to match your new entry with immediately adjacent cells above the one in which you are entering the information. It stops trying to match entries when a blank cell is reached. For instance, suppose you have information in cells A1 through A14 and A16 through A23. When you start typing an entry in cell A24, Excel only tries to match it with values in A16 through A23; the blank cell at A15 halts the comparisons.