LNK CTLR IS ADVISED LATER THAT INCORRECT HVY JET SEPARATION HAD BEEN APPLIED BTWN A C172 AND A MIL KC35R.

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THE TWR CTLR REQUESTED A 270 DEG HDG FOR A VFR ACFT DEPARTING TO THE W PRACTICE AREA. I APPROVED THE REQUEST. THE CESSNA CALLED INITIALLY DEPARTING THE ARPT CLBING TO MAINTAIN VFR CONDITIONS AT OR BELOW 4000 FT MSL. I IDENTED THE ACFT AND ALLOWED IT TO CONTINUE ON AN ASSIGNED HDG OF 270 DEGS. APPROX 1 MIN LATER; THE KC-135 DEPARTED ON A 300 DEG HDG CLBING TO 3000 FT MSL. I IDENTED THE KC-135 AND KEPT IT ON THE 300 DEG HDG AND CLBED IT TO 4000 FT MSL. THEN I INSTRUCTED THE C172 TO MAINTAIN VFR AT OR BELOW 3500 FT MSL. I THEN TURNED MY ATTN TO THE OTHER ACFT THAT I WAS CTLING. I OBSERVED THE KC-135 LEVEL AT 4000 FT MSL AND SEEING THE CESSNA WAS MAINTAINING AT OR BELOW 3500 FT MSL; I TURNED THE KC-135 TO A 170 DEG HDG FOR VECTORS TO AN ILS APCH. I WENT BACK TO WATCHING THE OTHER TFC. I HEARD THE CONFLICT ALERT GO OFF AND LOOKED FOR THE PROB. I OBSERVED THE CESSNA AT 3500 FT MSL AND THE KC-135 AT 4000 FT MSL IN THE SAME POS. I THOUGHT VFR VERSUS IFR; I HAVE 500 FT VERT; I CAN GO BACK TO WORKING THE OTHER TFC. I WAS NOT AWARE OF THE ERROR UNTIL THE NEXT DAY WHEN I WAS CALLED TO THE OFFICE. IN HINDSIGHT; I SHOULD NOT HAVE ALLOWED THE SLOWER ACFT TO GO AHEAD OF A FASTER ONE THAT WOULD CONFLICT LATER. OR; HAD I REMEMBERED THAT WITH A HVY ACFT I NEEDED 1000 FT; AS OPPOSED TO 500 FT; I WOULD HAVE EITHER STOPPED THE CESSNA LOWER OR CLBED THE KC-135 HIGHER BEFORE TURNING THE KC-135 SBOUND.