Vastly has 2 different meanings across 1 category:
Adverb
Adverb
1
to an exceedingly great extent or degree
"He had vastly overestimated his resources"
"was immensely more important to the project as a scientist than as an administrator"
2
Greatly, in a vast manner.
"The new software update vastly improved the app's performance compared to the previous version."