Formatting a flash drive after connecting to an infected PC?

Question

Malware

Hello. I connected a flash drive to an infected computer, decided immediately after that to format it in fat32 in a clean system, and then a strange, previously unnoticed behavior occurs - at first the free space on the flash drive is 4096 or 8192, and after a few seconds it changes to 12kb or 24kb and so on, then there are triples depending on the selected cluster size. And with another same 8GB flash drive formatted in a different system, this does not happen, the size remains the same as the size of the cluster, that is, 4096. What is it, could a virus get into the system in the first case and so disguise itself on flash drive?
upd. Literally the following is happening. If I format in ntfs:
cluster size 4096 bytes: free on flash drive 27992064 - in three seconds 27996160
cluster size 8192 bytes: free on the flash drive 27893760 - after three seconds 27901952 If
I format in fat32:
2048: free 2048 - after three seconds 6144
4096: 4096 - 12288
8192: 8192 - 24576
16384: 16384 - 49152 and so on
this is not a virus, but consistent behavior, but I want to understand why this happens with this particular flash drive, but not with others?