Bugs must be resolved efficiently for developers' limited resources. Bug reports are necessary for the bug modification process. Service user reports a bug as a bug report. Developer read bug reports and fix bugs. The developer can make discussion by posting comments on reported bug reports. There are several researches on the initial report of the bug report so that bugs can be fixed efficiently. But there are few researches on bug report comments. We focus on comments on bug reports. Currently, everyone is free to comment, but the modification time may be affected by how to comment. We investigate the topic of comments of the bug report. As a result of the investigation, the fact that the topics are mixed does not affect the modification time, however we found a tendency to shorten the modification time when the topic of the solution started early.