By default, a user on your Multisite will have a unique balance on each site they are a member of. Any points a user earns on site A will be credited to their balance on site A while points earned on site B will be credited to their site B balance.
Enabling the Central Logging feature will force your users to have one balance no matter which site a user is a member of. Furthermore central logging will log all point gains / losses on your website in your main sites log table only.
It is important to remember that the leaderboard shortcode presents results based on your central logging setup (assuming you are using Multisites). If the central logging is disabled, the leaderboard will only show results based on the balances that exists on the site where it is being used. This can result in “empty leaderboards” if no one has any points on the site.
If central logging is enabled, the leaderboard will adjust and present results based on your users global balance instead.
Please keep in mind that when presenting a leaderboard with central logging enabled, the results might be “unfair” if some users are members of more sites than others as this might give them a higher balance.
In order to use this feature, myCred must be enabled network-wide. Once you have set up your first point type on your main site, go to your Network admin area. Here click on the myCred menu and select “Enable” the central logging feature. Click the “Save Network Settings” button to save.
If you enable Central Logging after your users have already gained / lost points on your sites, their balance will not be added up into one new balance! Instead, their main sites balance will be accessible, all other balances will no longer be available.