By way of example, consider a fund holding USDC, BTC, ETH, SOL, MNGO, and SRM. All 6 asset spots are currently filled. If you would like to substitute SRM out for RAY, you will need to swap all SRM held out for USDC/another asset comprising your fund. With the SRM balance now zero, the token will no longer reflect, and you can add any new token to your fund.