you are not using all the arguments of the IF function: IF(logical test;value if true;value if false)
Your formula is missing the value if false! If you omit that, excel will display false if the logical test is not true.
You can try: =IF('Sheet1'!R8="Y",'Sheet1'!A8,"")
or: =IF('Sheet1'!R8="Y",'Sheet1'!A8,0)
|