Deleting photo on my phone

My Cloud Home - Personal Cloud Storage My Cloud Home
1

Why does deleting photos on my phone also delete the photos on mycloud home?

I thought it’s a back up system not a sync system.

Is there something that i need to set up in the setting??
Thanks for the help.

2

@Yapyap
What phone are you using, brand and model?

User Manual: My Cloud Home and My Cloud Home Duo (westerndigital.com)

3

iPhone 7