problem with differential backup and macros revision_no_max

Good morning , i have install comodo backup and run a full disk backup , then i have created a differential job that run only a day a week by selecting that specific base image.
The schedule was done inside the CB and i have added the macros revision_nomax01 because i want to rotate the differential backup having only one.
Both the full base image and the differential file are in the same directory.
At first run CB produced a differential file with a name similar to the base image but with a 00000001 at the end and this could be ok but at the second run that file was deleted and no other differential file was created , i have only the full base image with the original creation date.
What i’m doing wrong ? Is it correct to produce a base image and then a differential as explained?
My request is to have a base image that must no change and then have only one differential file.
Please let me know.