ICICI MONEY Multiplier bond bought from secondary market and held till maturity is to be treated as capital gains or interest income

As per brochure, ICICI Money Multiplier bond was originally issued for Rs.4,000/- in 1998, with the maturity amount of Rs.1 lakh in May 2023.
I bought this bond in October 2020 from secondary market for Rs. 80,000/- and held till maturity i.e. 1/5/23.
On maturity I was paid Rs.90,400/- after deducting TDS of 9,600/-
This gain of Rs.20,000/- is to be treated as Capital gains or interest income.
If it is capital gains, since Holding period was 31 months, can it be LTCG.
Pl clarify.