I've never once done a tax return so am not familiar with which form is which. Just knew it was illegal to declare more dependents than you have for tax purposes.
How many dependents you list on your W-4 is for the purposes of regulating how much federal taxes you want deducted from your paycheck - this is legal.
However, you are to list the ACTUAL number of dependents on your Form 1040 when you file your tax return.
Ask any accountant...they will tell you how this works and how it is legal to do so.