Two is a "couple" and more than two or three is several. If you eat four donuts you can say you had several but you may have had too many — especially if you get a stomach-ache. Several is a word that shows size or number when you can't be specific or when you want to summarize.
In this way, how many is several days?
By definition, “several” means three or more (but often less than “many,” which we will cover next). So, if several partygoers out of a group of nine were intoxicated, “several” could correctly be translated as three or four. If five partygoers were intoxicated, that would usually be stated as “most.”
What is the number of a few?
A few: More than one but less than maybe three to five.
Several: More than two but less than five or so.
A number of: More than two or three.
Is several more than a few?
“Several” is used to mean more than “some” but less than “many.” Again, there is no exact number. The dictionary says it means more than a few but not a great number.