Number of events found by "find_events" does not match the real number of events

I use the code
events = mne.find_events(raw, stim_channel='161_201', shortest_event=1, consecutive = False)
to find my events. My stimulus were images in which some were presenting for 0.45 seconds, while some were presenting for 3 seconds.

However, the results of this code usually has a little difference with my actual number of events. (for example one or two three extra events are found using this command).

What can be wrong here? How can I solve the solution?

Thanks in advance

So the duration of my stimulus presentation was different from image to image…