Spelled - spelt
The past tense of 'to spell' can be spelled either spelled or spelt. (See spell for an account of the irregular verb.) Both are pronounced the same way (IPA: /spɛlt/), and mean the same thing. Choose whichever you prefer the look of.
(There is also a rare noun spelt, which is the namme of a kind of wild wheat, and an even rarer noun meaning 'husk', with an even rarer verb meaning 'to take the husk off'. Choose spelled as the past tense of to spell if there is any chance of ambiguity. Such a chance is unlikely.)