I re-read my post later, and see that I should have said surviving spouse benefit. The terminology can get confusing.
To your question-
https://www.ssa.gov/planners/retire/agereduction.html
As I understand it: If lower earning spouse takes their benefit at 62, they will have a discount applied to their FRA benefit. Then the higher earning spouse takes their benefit at age 70. What will the surviving spouse benefit be?
If they are claiming on their own record, they would get 75% of their FRA amount. If they are claiming the spousal benefit, they would get 70% of the 50% benefit (or a total of 35% of the higher earning spouses FRA amount).
The surviving spouse benefit would be reduced because they claimed early. That reduction would be applied against the higher earning spouses amount (which is increased because of waiting to age 70).
So, they would get 75% (due to lower earner claiming early) of the 132% (due to higher earner claiming at age 70), or basically 99% of the higher earners FRA amount. If they had waited until their FRA to start, they would receive the 132% of the higher earners FRA amount.
All of these numbers are based on a birthdate from 1943 to 1954. The percentage numbers shift a bit as the FRA age was increased.