This is because history of your commands from current session are flushed on disk during logging off. And if you has been disconnected, when you connect again you will get last flushed history.
You can also manually flush history to disk by running:
history -d offset
history -anrw [filename]
history -p arg [arg ...]
history -s arg [arg ...]
With no options, display the command history list with line numbers. Lines listed with a * have been modified.
An argument of n lists only the last n lines. If the shell variable HISTTIMEFORMAT is set and not null, it is
used as a format string for strftime(3) to display the time stamp associated with each displayed history entry.
No intervening blank is printed between the formatted time stamp and the history line. If filename is supplied,
it is used as the name of the history file; if not, the value of HISTFILE is used. Options, if supplied, have
the following meanings:
-c Clear the history list by deleting all the entries.
Delete the history entry at position offset.
-a Append the ‘‘new’’ history lines (history lines entered since the beginning of the current bash session)
to the history file.
-n Read the history lines not already read from the history file into the current history list. These are
lines appended to the history file since the beginning of the current bash session.
-r Read the contents of the history file and use them as the current history.
-w Write the current history to the history file, overwriting the history file’s contents.
-p Perform history substitution on the following args and display the result on the standard output. Does
not store the results in the history list. Each arg must be quoted to disable normal history expansion.
-s Store the args in the history list as a single entry. The last command in the history list is removed
before the args are added.
If the HISTTIMEFORMAT variable is set, the time stamp information associated with each history entry is written
to the history file, marked with the history comment character. When the history file is read, lines beginning
with the history comment character followed immediately by a digit are interpreted as timestamps for the previ-
ous history line. The return value is 0 unless an invalid option is encountered, an error occurs while reading
or writing the history file, an invalid offset is supplied as an argument to -d, or the history expansion sup-
plied as an argument to -p fails.