Deductions & credits

Here, let me show you visibly how this works. See here

So, in this example, your total tax was 1,844.00. The EV credit wipes out the tax liability to 0. Youre withholdings will be completely refunded to you because the credit wiped out your tax liability to 0 already. Depending on what line 18 calculates to, that's going to be the amount that will be determined how much from your withholdings you will get back. For example, if Line 18,  would have been 10,000, your credit would have been 7,500(line 20). making Line 21 to be 2,500 tax liability. So,

in essence, the 4,000 from line 25 would wipe out your complete tax liability and thus you would only be refunded 1,500 (line 35A).