Hola Danny

The augmentative suffixes have a general rule but it doesn't always apply to all words, this is why we don't state any fixed rule in the lesson - the aim of the lesson is to learn that we use these suffixes to have an augmentative affect on some words and students can recognise them. 

This general rule I mentioned is: for nouns that end in a vowel, you drop that last vowel and add the suffix, for example: casa (house) -> casota and with nouns that end in a consonant, you keep the whole noun and add the suffix, for example: nariz (nose) -> narizota. 

As I said, the main thing is to recognise all these suffixes and their function.

Saludos

Inma