A PA28 CFI TAXIES OVER THE HOLD SHORT LINE FOR RWY 8 WHEN THE CTLR ADVISES THE ALREADY HOLDING ACFT TO 'TAXI UP TO AND HOLD SHORT OF RWY 8.'

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PREPARING TO DEPART BUR; I WAS CLRED TO TAXI TO RWY 8 AND DID SO; STOPPING AT HOLD LINE. I CHANGED FREQ TO LCL CTL; STATING I WAS READY FOR TKOF; RWY 8. THE LCL CTLR SAID 'TAXI UP TO AND HOLD SHORT OF RWY 8.' I TOOK THAT TO MEAN I WAS STOPPED TOO FAR BACK; PERHAPS AT THE FARTHER OF 2 HOLD LINES -- AN INST HOLD LINE; AND THAT HE WANTED ME TO MOVE UP TO A CLOSER; VFR; HOLD LINE. IT WAS MY MISTAKE NOT TO ASK FOR CLARIFICATION. I MOVED ACROSS THE HOLD LINE; WHEREUPON AN ACFT HOLDING BEHIND ME TOLD THE LCL CTLR; 'THAT AN ACFT IN FRONT OF ME IS ACROSS THE HOLD LINE.' THE LCL CTLR QUICKLY ISSUED A GAR TO A COMMERCIAL JET ON SHORT FINAL; AND AT THE SAME TIME I MADE A 180 DEGS AND TAXIED BACK ACROSS THE HOLD LINE. TWR REQUESTED A PHONE CALL; WHICH I MADE; AND THE SUPVR TOLD ME NO SEPARATION WAS LOST WITH THE SUCCESSFUL GAR; AND JUST WANTED TO KNOW IF THE MARKINGS HAD BEEN INADEQUATE; HARD TO SEE; ETC. I TOLD HIM ABOUT MY CONFUSION OVER THE LCL CTLR'S STATEMENT; AND THAT I RESOLVED NOT TO MOVE WITHOUT CLARIFICATION IN THE FUTURE.