There isn’t a clear and quick answer to this at the top of search engine results so I provide simple examples here:
.1e = scientific notation with 1 decimal point (standard form)
.2f = 2 decimal places
.3g = 3 significant figures
.4% = percentage with 4 decimal places
A more detailed explanation on the python string formatter can be found here: https://docs.python.org/3/library/string.html?highlight=string#formatspec (scroll down to table with e, E, f, F, etc. in the Type column)