It does indeed represent an amount.
I have four grapes in my hand. I open my hand and give them to you. How many are left in my hand? That’s the amount that zero represents.
According to Amir D. Aczel, author of Finding Zero: A Mathematician’s Odyssey to Uncover the Origins of Numbers, the oldest known inscription of the numeral and concept of zero is in Old Khmer (Cambodian) and dates from about 683 AD.
Zero is indispensable to our base-10 system of numbers because it allows numbers to have positional value. We take this system for granted, but remember, the Romans didn’t have it (hence Roman numerals). All computations that depend on place value (ones, tens, hundreds, etc.), even if not in base 10, require a zero as place-holder in order to work.