Karma is not based on our past actions alone. If we consider that time is not linear and that we arrive at this point of consciousness from any direction, then we must also consider future life karma. Could it not hypothetically be that you are suffering the consequences or reaping the benefit of a future action you have taken?
Karma is not a tit for tat as often understood. A person’s karma is in their attachments and their tendency to think and behave. When a child is born with certain prodigal gifts, it is attributed to the karma of having those gifts in a past life. If one causes harm to another through deceit, it may not necessarily be that they experience the exact same treatment but that they receive the karma of feeling separated from others or suspicious.
We change the trajectory of our future lives by changing our present karma, altering the samskaras (impressions/imprints) in our consciousness.
What it all leads to is the present. You change your past life karma by changing yourself now, and you change your future life karma by changing yourself now.
Focusing on now, all else is simply once again idea or projection.