The hashrate is not 300 MH/s over 24 hours. There were miners mined at stopped mining over the past 24 hours. 300 MH/s is just the current hashrate.
The current running round with 0.34 BTC invested and 300 MH/s is 3.
The link here: http://multicoin.me/history/2 shows the finished round which is round 2. There was 4.06 Bitcoin invested and 2.85 BTC generated from miners that round.