it looks like you have 2 low spots both on the left and right sides about 1/4 down from the top as pictured.
as you scrape off the tops of the peaks, the lower peaks will start to emerge.
as you get ever flatter, the blue dots will increase in size until the entire angle plate could become blue if you were to scrape it long enough.
you should be happy with 40-60% blue and 20 to 40 Points per inch dependent on use or purpose.
it's pretty flat right now as it sits.
consider this,
even if you scraped it to a tenth, had 60%, and 40 PPI...
as soon as you wrench down on it with a clamp, it will distort the work as well as the angle plate and any superfluous accuracy will be negated anyway.
trust me, you can spend hundreds of hours chasing perfection.
you'll have to be your own judge when it comes time to quit scraping on a piece, or if one more pass will do it.