The look up value and the value in the table are probably different formats. One of them is probably formatted as a number, while the other is formatted as text.
if you find a cell with a number of 1 (or make one). Copy it, and highlight all numbers, Paste Special > Multiply which will convert numbers stored as text to numbers.
If you haven't formatted the cells, text will also be left justified, while numbers will be right justified. Hope that helps!