If you have a Tagbox/Category "2000 - 2010" and then type this in as a search term or select the search suggestions then the assets in this category will not be found by the simple search.
The minus is a search operator in Picturepark. When there is a space in front of it the search interprets this as you wanting all assets tagged with 2000 but not 2010 so anything tagged with 2000 - 2010 will not be found.
You do have several other possibilities:
Not use any spaces e.g 2000-2010 - I would recommend this option.
Using the space only after the hyphen e.g. 2000- 2010
Use EN-dash (Alt + 0150 Windows)
Use EM-dash (Alt + 0151 Windows)
While a space between the hyphen and the year may look better - technically in English spaces are not used when using hyphens: https://jakubmarian.com/hyphen-minus-en-dash-and-em-dash-difference-and-usage-in-english/.