B737 FLT CREW REPORTS CONFUSION OVER MEL ON NUMBER 1 LE FLAP TRANSIT LIGHT.

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UPON ARR AT THE GATE THE RELEASE STATED 3 MEL'S; ONE OF WHICH WAS XX-X. RELEASE STATED FORWARD LEADING EDGE FLAP TRANSIT LIGHT AND #1 OVERHEAD SLAT INDICATOR. CHKED LOGBOOK FOR ALL 3 MEL'S AND THOUGHT ALL WERE GOOD. THE WRITE-UPS WERE FROM THE NIGHT PRIOR. CALLED DISPATCH TO CONFIRM THAT THE FLT PLAN WAS PLANNED AT 300 KTS AND .65 MACH AS PER MEL XX-X. ENRTE (2+35 HR FLT); CHKED LOGBOOK AGAIN AND SAW IT WAS THE #1 LEADING EDGE FLAP THAT HAD BEEN WRITTEN UP AS TRANSIT ON THE OVERHEAD PANEL. CHKED MEL AGAIN AND THOUGHT ALL OK; IN FACT BETTER; BECAUSE THERE IS NO .65 MACH SPD RESTR WITH A #1 FLAP AS LONG AS THE FORWARD PANEL LEADING EDGE TRANSIT LIGHT AND OVERHEAD LIGHT WORKED PROPERLY. AFTER ARRIVING; MAINT SAID THE LEADING EDGE FLAP IS NON-DEFERRABLE AND WE SHOULD NOT HAVE LEFT. AFTER READING THE MEL MULTIPLE TIMES; I STILL AM NOT SURE OF THEIR INTERP. DID I INTERPRET THE MEL WRONG OR IS IT JUST MAINT POLICY TO NOT TO DEPART A MAINT BASE WITH THIS CONDITION? REGARDLESS; MAINT FIXED THE FLAP AND REMOVED THE MEL XX-X. WE CONTINUED ON. MEL XX-X HAS TO BE THE MOST OR ONE OF THE MOST; CONFUSING MEL'S IN OUR OP. REWRITE THIS TO MAKE IT CRYSTAL CLR IF POSSIBLE.