SMT TWIN PLT PANIC WHEN INSTRUCTED BY TWR TO QUICKLY CROSS A PARALLEL RWY; TURN L AND TKOF RESULTED IN TKOF ON THE PARALLEL RWY ON WHICH HE WAS TO QUICKLY CROSS.

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GND INSTRUCTED ME TO TAXI TO RWY 30L N INTXN. AFTER GOING TO TWR I WAS INSTRUCTED TO IMMEDIATELY CROSS RWY L TURN AND CLRED TO TAKE OFF RWY 30R. I DID NOT UNDERSTAND AND I SAID SO. VERY QUICKLY THE TWR SAID; 'I SAID CROSS RWY IMMEDIATELY TURN L CLRED TO TAKE OFF (RWY 30R).' I'M NOT SURE HE SAID RWY 30R; BUT IN RETROSPECT I THINK SO. I IMMEDIATELY TURNED L ONTO RWY 30L AND DEP. AN AIRLINER ABOUT 1500 TO 2000 FT HAD TO GAR. I DIDN'T FULLY UNDERSTAND MY INSTRUCTION THE SECOND TIME. I PICKED OUT THE 'IMMEDIATELY' AND 'TURN L' AND ACTED. THE SECOND INSTRUCTION FROM THE TWR HAD A SENSE OF URGENCY AND I REACTED TOO QUICKLY EVEN THOUGH I DID NOT FULLY UNDERSTAND THE INSTRUCTION. I WAS SURPRISED BY THE IMMEDIATE INSTRUCTION THE VERY INSTANT I CONTACTED TWR. I SHOULD HAVE ORIENTED MYSELF BETTER BEFORE CONTACTING TWR (IE ACFT ON FINAL; RELATION OF RWY 30L AND R ETC). SOMEHOW THE INSTRUCTION TO TURN L MADE THE INSTRUCTION MORE DIFFICULT TO UNDERSTAND. THIS WAS THE FIRST TIME I HAVE EVER DEP THE WRONG RWY AND I WILL DO MY BEST TO MAKE SURE IT WILL NOT HAPPEN AGAIN.