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The rule with regard to meal offerings is that the parts of the offering that are eaten by the kohanim are permitted to them only after both the kometz – the fistful of flour taken for sacrifice – and the levona – the frankincense – are placed on the altar.
The Mishna on our daf discusses whether having an inappropriate thought about eating the meal offering – that is, planning to eat it when it is forbidden to do so – will disqualify the offering if it happened only when sacrificing just one of these elements. According to the Ḥakhamim, it is only if the inappropriate thought occurred during both the sacrifice of the kometz and that of the levona that the offering will become piggul and the person who eats of it will be liable to receive karet – excision (a Heavenly punishment). Rabbi Meir rules that an inappropriate thought during either one of those times will suffice to disqualify the offering.