It appears to be a log entry from a ham radio operation. Here's a breakdown of the information:

* "04:55" indicates the time of the entry in 24-hour format.

* "JF7RJM/7" is the callsign of the station operating, with the "/7" indicating that it's an amateur radio operator with a prefix of JF7. The number 7 suggests that this is a local or regional operation within Japan (where the suffix JT would typically be used).

* "on JP-1075(Mogamigawa Prefectural Nature Park)" indicates the location where the transmission was received, which appears to be within the Mogamigawa Prefectural Nature Park in Japan. The number 1075 is likely a unique identifier or grid square for that location.

* "JP-YT" is another way of specifying the location, using an international standard grid system (ITU-R Grid Square).

* "18100.0 FT8 [JF7RJM]" indicates that this was a transmission in the FT8 mode on a frequency of 18.100 MHz.

In summary, this log entry reports a ham radio transmission from JF7RJM/7 at Mogamigawa Prefectural Nature Park, Japan (JP-YT), operating in FT8 mode on 18.100 MHz.