Only some of your Social Security benefits are taxable (although it can be up to 85% of them).
It's a slightly complicated formula, but if you take 1/2 of your Social Security and add your other income (IRA distributions, odd jobs, etc.), then if the sum is less than $32,000 (married filing joint), then your Social Security is not taxable at all. If this sum is a little more than than, then there is a sliding scale to see how much is taxable (up to that 85%).
So, depending on other factors such as how much other income you had, these numbers are perfectly possible. You can read about this at the IRS website. Note that this webpage is from 2017, but I don't think that the computation has changed for 2018.
