If they've had enough at any point in the meal it's totally fine some days they will want more others done. They may get cross or fussy or simply stop opening there mouth for the spoon. Don't put any pressure on it just make sure they aren't tired at meal times too
Honestly, a few spoons at this stage is more than enough. Remember that they are used to just milk, so the heaviness of actually food will fill them up so easily. Fussing throwing the food/spoon/bowl are all signs of them being finished.
We take signs of fussing and just being fed up as she is done and content. Food isn’t really a big deal until they are older anyways so it’s just the exposure to the textures and flavours etc.