Why redis db should be less than 11

[U8F69]

I'm using db 11 for AFFiNE and the start up is blocked now

db: {
    desc: 'The database index of redis server to be used(Must be less than 10).',
    default: 0,
    env: ['REDIS_SERVER_DATABASE', 'integer'],
    shape: z.number().int().nonnegative().max(10),
  },