Grande Lata (Big Can) is a portuguese expression that we use when we think something is unfair or it is demanding too much. For example, you arrive on time to an interview and your friend arrives 1 hour late, but he goes in first because he is a friend of the dentist. You have the right to exclaim: grande (or "granda") lata!
This place has big BIG ham and cheese toast for 3.25€ (and for two people it's enough). It is kind of a café/roulotte near the river and the Electricity Museum, nothing "out of this world" but good to put the conversation up to date, and common: the river, a cheap toast, good company, café au lait and a walk through Belém, one of the most beautiful places in Lisbon. Sounds good to me.