How to add watermark ffmpeg multiple duration?

I'd like to ask,

how to add watermark few seconds and many duration ?

for example I have a 10 minute video, I want to show the watermark for 15 seconds at 05:26 minutes then after 15 seconds the watermark will disappear, and I want to show the watermark again at 08:15 minutes for 15 seconds and I want to add another watermark for 30 minutes seconds at minute 09:30 ,

How to ? I don't know the command