Retirement tax questions

Both W-2s (married filing jointly) show box 4 is precisely 6.2% of box 3. There is nothing I can see on either W-2 that would indicate a deferral. My W-2 box 3 is at maximum and my wife's box 3 is the same as box 5 (medicare wages). I will ignore this as I agree it has nothing to do with IRS filing.