Roe allowed abortion in the first trimester, in most states where the limit was set based on Roe, this was 15 weeks. The Dobbs case, the one in which Roe was overturned, was a suit brought by abortion activists (Jackson Women's Health Organization v Dobbs, Georgia), where they were objecting to the 15 week limit and trying to extend Roe until 24 weeks. It backfired and Roe was overturned.
At 24 weeks a fetus has a 67% chance of surviving outside of the women and is considered viable in most states. The state in where this occurred allows abortion up to 20 weeks.