Your sentence means "I've recently eaten a burrito."
If you wanted to mean "I've only eaten a burrito" the "just" goes after the verb.
e.g. "I've only eaten just a burrito.", or another example: "He bought just one chocolate bar."
Your sentence means "I've recently eaten a burrito."
If you wanted to mean "I've only eaten a burrito" the "just" goes after the verb.
e.g. "I've only eaten just a burrito.", or another example: "He bought just one chocolate bar."