Special Surrender Value is what the insurer offers above the regulatory minimum, based on its own actuarial assessment of the policy's accumulated reserve. SSV is not a fixed formula — each insurer publishes a Surrender Value Factor (SVF) table that increases with policy year.
For LIC endowment plans, SSV typically exceeds GSV from year 5 onwards, and from year 8 onwards is materially higher. The actual surrender payout you receive is the higher of GSV and SSV, plus the discounted vested bonus.