May a make two (edit: three) suggestions:

a) write "2000 f." for 2000–2001 like common for giving page numbers in citations.
(I just learned that "f." is for giving someone’s birthdate in Swedish 😁 )
en.wiktionary.org/wiki/f.#Adje…

b) Use "≤" or "≥" mathematical operators. As the key is most probably read from the top to the bottom maybe give the lower number year instead like
- ≥ 2023
- ≥ 2021
- ≥ 2019
- …
- < 2000

c) short form 2000/01 to 2023/24