ALT DEV ALT EXCURSION IN A CLRNC INTERP PROBLEM.

Narrative

CLBING OUT OF PDX ON ASSIGNED HDG OF 040 DEG I WAS TOLD TO CONTACT DEP. ON INITIAL CONTACT WITH DEP I WAS TOLD TO RESUME OWN NAV. I THOUGHT THIS WAS ALSO LIFTING THE ALT RESTRICTION OF 1500 FT. HEARING THE WORDS 'RESUME OWN NAV' MANY TIMES; I FORGOT AND ASSUMED ALSO 'APPROPRIATE VFR ALT' BUT I WAS MISTAKEN. WHEN CTLR ASKED WHAT ALT I WOULD BE FLYING AT I SAID 2200 FT. HE ASKED IF I WAS ASSIGNED 2000? I TOLD THE CTLR ON INITIAL CONTACT/CLRNC DELIVERY ASSIGNED 1500 FT. THE CTLR STATED; RESUME OWN NAV; SAY ALT CLBING TO. I TOLD HIM 2200 FT. I ASSUMED; ONCE RESUME OWN NAV WAS STATED I COULD CLB. I STARTED TO DSND BACK DOWN WHEN HE STATED TO ASK QUESTIONS. NOTHING MORE WAS SAID ABOUT THIS AND HE ASKED ME WHEN I WAS GOING TO COME BACK TO PORTLAND. THINGS GOT VAGUE BTWN MYSELF AND THE CTLR. I SHOULDN'T HAVE ASSUMED. I SHOULD HAVE STAYED AT 1500 FT. TEST FLT IN FOREIGN ACFT; WATCHING SYS. I CALLED TRACON AND HE EXPLAINED THE PROC THAT WHEN 'RESUME OWN NAV' IS STATED THAT IS NOT AN ALT CLRNC TO CLB.