mergeHistograms problem

I made two folders under my run folder like /g4see/run/SRAM and /g4see/run/SRAM1. Then I ran different cases under the two folders. Then I first used mergeHistograms under /g4see/run/SRAM1 through “mergeHistograms ./”. It worked well. But when I continued to use “mergeHistograms ./” under /g4see/run/SRAM folder. It seemed not only output files under /g4see/run/SRAM were merged, but also output files under /g4see/run/SRAM1 were also included.
I want to know why this happened. Thanks!