What are these database columns in core_members

[Aetherdan]

There are two columns I would like to understand better.

joined appears to be a long number, how does it convert to actual joined date?
ANS: Just realised its the unix time stamp.

members_day_posts appears to have a rather long number in there with a comma. How does this work?
It appears to be {#},{Joined Date} What is the #? Posts today? or Posts average?
ANS: Just worked it out, its posts made today followed by the join date.

[Aetherdan]

1) Unix time stamp.

2) Number of posts made today followed by the join date.

[Aetherdan]

Apparently members_day_posts isn't what i originally thought it was. Any help?

ANS: The value of members_day_posts is {Number of posts}, {for last day online as unix timestamp}

[Martin A.]

The "members_day_posts" is used by the "Posts per day" setting, as a way to measure how many posts a member has posted the last 24 hours. You've guessed the parts right, before the comma is the number of posts, after if the unix timestamp from the start of the measurement period. The period starts when the first post is made, and lasts a minimum of 24 hours. 

The number of posts or the unix timestamp is not automatically updated if the member is not online, so don't use the number of posts for statistic purposes.