According to TzScan.io, in the "rewards" TAB, if we sum the percentages of the "Share" column, we get always a value lower than 100%. I would like to understand how the earnings of a baker are distributed to its delegators. Is it correct to assume an aprox. 40-60% ratio of what stays for the baker and what is distributed as rewards to its delegators?
You also need to take into account the (evaluated) balance of the baker on the tz1 address, which also generates rewards, but which are not stated under the rewards tab. Under the rewards tab, only the KT1 addresses of the delegators are shown. It is not uncommon for a baker to own 40% of the total stake, so I don't think there is anything suspicious here.
Delegators always receive rewards in relation to their amount delegated to the baker, not in relation to the total stake.