EXEMPTIONS ON CAPITAL GAIN

Sir

a person has purchased a flat from builder 3 yrs back 2021 and paid full amount . he has got allotment letter from builder also. the registration has been done only in june 2023. now the person has sold his flat in may 2024. will this be considered as long term or short term. since allotment letter and payment fully made in 2021 can this be taken as long term. pl guide