Yeah you want to count the cases such that (in pseudo-code)
`today - A_MONTH < edd < today + A_MONTH` which is equivalent to
`today - 2 * A_MONTH < edd - A_MONTH < today`
which fits the general form
`today - window < emitted_date < today`

So the emitted value is `edd - A_MONTH` and the window is `2 * A_MONTH`.