@tanguatlay,
It means one slept early or late in the previous night. It can be perceived using the reader's preference.
If one sleeps late it is likely they got up late also, and if one sleeps early it is likely they got up early.
The sentences have enough elements to be generally understood.
They are not precise or detailed but they are specific enough to get the gist.
Though not all complete sentences have clarity and clarity should generally be a prerequisite for what a sentence is comprised of.
By allowing sentences without clarity then sentences can become figures of speech where the hearer must interpret their true meaning.
Complete sentences can be vague enough to be ambiguous, this is a form of creative writing.
I went to bed late (for what)?
That is the figure of speech, emphasis by omission. "Paralipsis"