How many categories and subcategories can I select for one attribute?

I have created Attribute: Condition

And I was able to select only 250 subcategories, no longer allows it to be saved in one attribute. how to fix it. I need to add about 20 subcategories more.

@Olegs
For table t_attribute you may need to increase length of field s_category_id (from varchar 1000 ideally to varchar 5000)