Help understanding the function VALUES when passed as a filter parameter in Calculation in Dax

Hi,

When you write 

CALCULATE(
  [Sum revenue],
  'Product'[ProductID]>10
)

DAX actually goes away and does this:

CALCULATE(
  [Sum revenue],
  FILTER(
    ALL('Product'[ProductID]),
    'Product'[ProductId] > 10
  )
)

 eg it removes any existing filters on product id (eg the ones coming from the matrix rows and then it adds a new filter to just get ids greater than 10.

In the measure that is working it does the same but VALUES('Product'[ProductId]) add back the existing Product Ids that were in the filter context to start with.