I believe the score of 5 is the minimum requirement to prevent a case where there are less than 50 serious participants, (e.g. if 40th place and below have score of 0) which was the case before the deadline extension.
Also, the “score” in that context is the floor level, not the reward. (This also can be found in Section 11) So you need to get higher than 5 in terms of “Mean number of Floors” but seems like you only scored 4.8… won’t hurt to confirm with the host though.