The family contribution limit is shared between you and your spouse. If you are married and your spouse made a $3,750 HSA contribution, only $3,750 of family limit remains for your own HSA contributions. If you and your spouse are both HSA eligible and one of you has family HDHP coverage, both are treated as having family HDHP coverage.
If you are not married or your spouse has made no HSA contribution, you've apparently somehow told TurboTax that you have self-only HDHP coverage rather than family coverage. Revisit the HSA section and review the calculations on any Forms 8889 present in your tax return.
