Why run-with-timer generates so many timers?

[address@hidden]

I write an extension rainbow-fart.el (
https://github.com/stardiviner/emacs-rainbow-fart)

Here is the code lines which running timer:
https://github.com/stardiviner/emacs-rainbow-fart/blob/master/rainbow-fart.el#L245

When I run command `list-timers`. I found many timers is generated by
rainbow-fart.el

#+begin_example
275.87      900.0    rainbow-fart--timing-remind
278.20      900.0    rainbow-fart--timing-remind
280.55      900.0    rainbow-fart--timing-remind
280.65      900.0    rainbow-fart--timing-remind
280.66      900.0    rainbow-fart--timing-remind
280.74      900.0    rainbow-fart--timing-remind
280.86      900.0    rainbow-fart--timing-remind
280.94      900.0    rainbow-fart--timing-remind
281.14      900.0    rainbow-fart--timing-remind
281.19      900.0    rainbow-fart--timing-remind
281.21      900.0    rainbow-fart--timing-remind
281.28      900.0    rainbow-fart--timing-remind
281.81      900.0    rainbow-fart--timing-remind
281.89      900.0    rainbow-fart--timing-remind
283.31      900.0    rainbow-fart--timing-remind
283.39      900.0    rainbow-fart--timing-remind
285.49      900.0    rainbow-fart--timing-remind
.....
#+end_example

Is my `run-with-timer` source code wrong? Or did I misunderstand this
function?

Hope experts like you can explain it for me, thanks very much.

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