Received CP21B and got the refund of $5130 which is bigger than I thought. Did IRS include what I want 2020 refund to apply to 2021 estimated tax amount of $2300?

Only the IRS can answer your questions concerning the amount received and any changes made to your tax return.

Go to this IRS website for information on a CP21B notice - https://www.irs.gov/individuals/understanding-your-cp21b-notice