Good day!
Dear Luis!
I assumed and still assume the following algorithm.
We shouldn't substitute two concepts:
1. Make one full every
2. Differential copies to keep
Will explain.
The option that you propose is absolutely normal. But the question. Why then field Differential copies to keep? If we set the value 6 in the Make one full every field, then it is clear that all copies between full copies will be stored.
And I'm talking about STORAGE! To restore information, we need to have the last full backup and the last differential backup. So we will store the last 2 differential backups. And make full copies after the specified number in the Make one full every field. I tried to explain in the pictures.
So. The first execution in the task is a full backup (in the picture # 1). Then differential and so on 6 times until complete. The second execution in the task is differential (in the picture # 2).
The third is differential (no. 3). But while maintaining the fourth execution (on picture No. 4), it should replace No. 1. The fifth is to replace the second. The sixth is the third. Etc. As a result, we should get such a structure.