Based on the details you have given here, it does not compute.
I would suggest that you make an appointment with a local Social Security office and go over your late father's benefit amount.
You should try to find out the details of his benefit - perhaps his last Social Security Statement of earnings that is issue at the end of the year for those who need it for taxes and other type of documentation.
Here are some possibilities which I am just guessing about -
From your details, your late father's benefit amount was VERY low. Extremely low. This could occur IF your late father only worked a few years, 11 years is the minimum OR he earned a VERY low amount during the (up to)30 years which he worked. Since 1973, SS has used a different formula for people in this type of situation - it is rarely used anymore - but that only could explain his LOW benefit but not why your Mom is getting this extra amount as a Widow benefit.
What might make more sense is that your late father was not drawing his own SS old age benefit - possibly he never filed for his own benefit. The amount he was getting was something else - like perhaps it was an SSI benefit rather than his SS old age benefit. Or perhaps he was drawing a spousal benefit based on your mother's earned benefits and never filed for his own.
Or something else could have been deducted from his SS old age benefit and you are referencing just the monthly total.
- Perhaps for some reason he didn't have enough time and contributions to Medicare Part A and he was having to pay for it. It is premium free for most people who have worked and made contributions during their work life but if not, the cost of it can be upwards of $400 a month, prorated based on what you did contribute during those working years.
- He could have owed the IRS or some other government entity some money and they were collecting out of his SS old age benefit.
Based on your details, I am just guessing about why his benefit could have been so low but you are right, the maximum widow/widower benefit for those who are full retirement age is what the deceased person would do have received. The amount can be made up of the living spouses old age benefit + an additional amount from the deceased person to equal this maximum amount, which seems to be what SSA is saying.
BTW, the death benefit amount for SS is $255, not $225, and it has been this amount for a good while.
Seems to me that you have to figure out why your late father was only getting a benefit of $500-something a month and what type of benefit it was. Remember Medicare Part B premiums and sometimes Medicare Part D premiums are deducted monthly for most everybody if they are not on some Low Income Subsidy. This should also show on that yearly statement.
Good Luck in figuring out this mystery - I have worked on several that you wouldn't believe.
It's Always Something . . . . Roseanna Roseannadanna