Now, when I looked at a few profiles there were two cases:

Some customers received the email, didn’t open it and placed order. Does this placed order value reflect in my campaign analytics? -- The default attribution for Klaviyo accounts works on emails that are opened or clicked, so if it wasn’t opened, that email would not get revenue attribution.
You can check he attribution settings on your Klaviyo account under Settings → Email → Attribution, and you can update the conversion window and how to attribute conversions

Second, a customer received my email, opened it, didn’t order anything, he was then targeted by my active on site flow email, he opened it and placed order. Now, is this placed order value attributed to my campaign email or my flow email or both? --The revenue will be attributed to the most recently opened or clicked email, in this case, that would be the active on site flow email. 

Hi @USMarketer thanks for posting in the Klaviyo community! I see how the revenue attribution could be confusing.  

Now, when I looked at a few profiles there were two cases:

Some customers received the email, didn’t open it and placed order. Does this placed order value reflect in my campaign analytics? -- The default attribution for Klaviyo accounts works on emails that are opened or clicked, so if it wasn’t opened, that email would not get revenue attribution.
You can check he attribution settings on your Klaviyo account under Settings → Email → Attribution, and you can update the conversion window and how to attribute conversions

Second, a customer received my email, opened it, didn’t order anything, he was then targeted by my active on site flow email, he opened it and placed order. Now, is this placed order value attributed to my campaign email or my flow email or both? --The revenue will be attributed to the most recently opened or clicked email, in this case, that would be the active on site flow email. 

This article has more information about how attribution works in Klaviyo. Hope this helps!