This point refers to what was left, rewards-wise, from the previous budget of that network. Unspent incentives that carry to the following month.
As of today there’s around $11M in stDOT TVL. Like mentioned on the budget and on the previous comment, incentives overall have been getting consistently reduced (Sep, Oct, Nov, Dec, to track progress). They are getting especially reduced on these lower usage/growth/tvl networks like you mentioned.
The way it works is that Lido has a reWARDS Committee of eight people who plan and propose these budgets to the DAO each month. Then the motions to fund the balances for each month’s incentives go through a governance process called EasyTrack, in which voters and the Lido DAO have the ultimate say and can object.
Most of these rewards serve to incentivize liquidity providers in stAsset pools. The deepest pools in DeFi are (w)stETH’s, making it the most liquid ETH liquid staking token. This is one of the key advantages because it ensures stakers can enter and exit stETH positions up to very large sizes and that the integrations (mostly as collateral) work and are useful.
Hope that helps and thanks for questioning