DC-65 LANDS OUT OF SEQUENCE AT LVK.

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15 MI NW OF ARPT; I CALLED IN FOR LNDG. WAS TOLD TO APCH FROM THE SW AND RPT A 1 MI L-HAND 45 DEG ENTRY TO THE S PARALLEL RWY. CTLRS WERE EXTREMELY BUSY DUE TO TFC FOR THE 2 RWYS. I OVERHEARD A CTLR TELL ANOTHER ACFT THAT I WOULD BE MAKING A DOWNWIND ENTRY (INSTEAD OF THE 45 DEG ENTRY AS INSTRUCTED). DUE TO FREQ SATURATION; I COULDN'T CONFIRM IF I WAS TO MAKE DOWNWIND OR A 45 DEG ENTRY. WHILE EXECUTING THE 45 DEG ENTRY; WAS TOLD TO 'FOLLOW THE DECATHLON AND CLRED TO LAND.' NOTE: I WAS NOT TOLD 'YOU ARE #2 CLRED TO LAND' WHICH IS THE USUAL PHRASEOLOGY FOR LNDG IN SEQUENCE. AT THAT TIME THE DECATHLON WAS ON A L XWIND DEP CLBING TURN. I WASN'T SURE IF THE DECATHLON WAS STAYING IN THE PATTERN OR DEPARTING. I STAYED BEHIND THE DECATHLON ABOUT 1 MI. THE PATTERN ALT IS 1400 FT AND THE DECATHLON CLBED 300-400 FT ABOVE THAT AND THEN ANGLED OFF TO THE SE WAY OUTSIDE OF THE NORMAL PATTERN. DUE TO FREQ CONGESTION; I COULD NOT CONFIRM WITH THE TWR IF I WAS TO CONTINUE FOLLOWING THE DECATHLON OR LAND AT MY DISCRETION. HAVING RECEIVED THE COMMAND 'CLRED TO LAND;' I LANDED AND WAS THEN TOLD BY TWR THAT I HAD LANDED OUT OF SEQUENCE. CONCLUSION: THE CTLR'S COMMAND; 'FOLLOW DECATHLON; CLRED TO LAND' IS CONFUSING. IF THE CTLR WOULD HAVE SAID 'FOLLOW DECATHLON; #2 CLRED TO LAND;' THERE WOULD BE NO DOUBT ABOUT WHAT I WAS TO DO. ADDITIONALLY; FREQ SATURATION DID NOT ALLOW ME TO CONFIRM THE LNDG REQUEST. I REVIEWED THE AIM THAT EVENING TO VERIFY THE PHRASEOLOGY 'FOLLOW...AND CLRED TO LAND.' THE PHRASE '#2 TO (TKOF OR) LAND' IS LISTED AS AN EXAMPLE. IF THIS SIT ARISES IN THE FUTURE; I WILL CONTINUE IN THE PATTERN UNTIL ABSOLUTELY SURE OF THE CTLR'S COMMAND. THE WORST IS THAT I WOULD HAVE A VERY LONG EXTENDED DOWNWIND.