A C172 CROSSED THE ACTIVE RWY WITHOUT A CLRNC AT DAB.

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DAB GND CTL WAS EXTREMELY BUSY AND THERE WAS HVY FREQ CONGESTION. I WAS GIVEN THE FOLLOWING INSTRUCTIONS WHILE #1 HOLDING SHORT OF RWY 25R ON RWY 16 AWAITING TAXI INSTRUCTIONS TO RWY 25L. MY ACFT FOLLOW CESSNA (WHICH HAD JUST CROSSED RWY 25R FROM IN FRONT OF ME) CONTINUE TO HOLD SHORT RWY 25R WHICH I AND MY CFI STUDENT HAD NEVER HEARD. I LEARNED THIS AFTER LISTENING TO THE TAPE AT THE DAB ATC FACILITY. HAVING BEEN TOLD TO FOLLOW CESSNA AND CONTINUE WHEN I WAS AT THE HOLD SHORT OF RWY 25R LINE; I LOOKED AND CLRED TFC L AND R AND CONTINUED. I SAW NO TFC IN EITHER DIRECTION. I ALSO QUERIED MY CFI STUDENT FOR CONFIRMATION ON CLRNC TO CROSS RWY AND HE CONFIRMED THAT WE WERE CLRED TO CROSS RWY. IN HINDSIGHT; I SHOULD HAVE DOUBLECHKED WITH GND CTL TO CONFIRM; EVEN THOUGH THE FREQ WAS VERY CONGESTED. IN ADDITION; I FEEL ATC SHOULD NOT GIVE CONTRADICTORY SOUNDING CLRNCS; IE; WHILE AT HOLD SHORT. IN DISCUSSING THIS WITH ATC; THE CTLR OR HIS SUPVR ADMITTED HE HAD THOUGHT I WAS #2 AT HOLD SHORT LINE AND NOT #1 WHEN HE ISSUED MY INSTRUCTIONS.