I can't remember, but you might try this site: https://resources.allsetlearning.com/chinese/grammar/Expressing_%22excessively%22_with_%22tai%22 or this one: https://www.chineseboost.com/grammar/le-grammar-summary/

Basically 了 in this context is being used as the "intensifier particle." Think of it like how 吗 acts like a question mark 了 acts like an exclamation point.

I've also noticed since a female voice has replaced the male Chinese speaker, sometimes she says 'Le' and other times what sounds like 'Lao'.

These two Chinese girls on Youtube are very good at explaining all the different uses of 了.

www.youtube.com/watch?v=JjAGEjr6-kY