I assume you're asking why the e is removed when the suffix -ment is appended. There are no fixed rules that I'm aware of, but here's a general rule of thumb:
The suffix -ment and -able don't often change the pronunciation of the root word.
The e from manage doesn't get removed because it will chang the pronunciation of manage:
- manage + ment → management
the pronunciation doesn't change because the e is there to make the g soft (/d͡ʒ/)
But if you remove the e:
- manage + ment → *managment
it will change the pronunciation of the word i.e. g usually represents a hard g sound (/g/) before a, o, u and another consonant.
In argue, the final e is there because English words don't often end in a u (or v).
In argument, there are other consonants after the u so we don't need the e:
Another example is:
- notice + able → noticeable not *noticable
you can't remove the e because if you removed it, you'd get noticable with a hard c sound (/k/)
Updatable and updateable both are correct because the removal of the e doesn't change the pronunciation of the root word.
In summary, if the removal of the e changes the pronunciation, keep it, otherwise remove it.