We have already reached to iPhone device limit so we are not able to add new iPhone to our developer accounts device list.
We have renewed our membership for our apple's developer account.
and it is asking us to reset our device list.
but when we proceed to reset device list, but we are not able to remove device from device list.
but on next page it is not changing the count of no of devices able to register
So it is confusing for me will it remove the deselected devices and let me add new devices instead of them or the it will just disable them.
I'm about to go through same process. The page is somewhat confusing unless you read all the info carefully. Those devices you check will be carried over and will keep counting towards total device count. Those devices you uncheck will be removed.
However, when I uncheck all the devices, I get this:
This is super confusing. If I'm removing all the devices, I'm expecting the count to go all the way up to 100 again. Unless it tells me the count before reset, in which case this information only confuses the user, I want to see what device counts I get after I reset.
Update
So I went ahead and reset the list.
Once you do that, you get this page:
So apart from a bit confusing message before hitting reset, it works OK.
Just need to remember that to remove a device you need to uncheck it.
Your acknowledgement says that, once you reset devices after that you can not reset device in until one year or you renew your developer account again. You can disable any device but it is count in your maximum device limit you can say 100. That's it!
You should refer Apple - Resetting your Device List,
If you are the Team Agent for your Apple Developer Program team, you can reset your list of development devices each year using Certificates, Identifiers & Profiles. You can register up to 100 of each device type for testing and Ad Hoc distribution per membership year. At the start of your new membership year, you and any Admins on your team will be presented with the option to remove listed devices and restore the available device count to 100 when you first sign in to Certificates, Identifiers & Profiles.
Although you may remove a device from your account during the year, it will continue to count against your device limit. When resetting your list, make sure to remove all devices you no longer use for development before adding any new devices.
Unchecked devices will stay with your developer account. Checked devices will be removed from your account. So check the devices you want to disable or no longer needed. Then check acknowledge button and click to Reset button to reset the device list. Let me know if that makes sense.
Please remember as said in the acknowledgement box that, during this membership year these disabled devices will be counted as total number of devices you can add in your profile.
You can still add device even the list is full. Just connect your device and run your app on Xcode. A prompt will pop-up and click "Register device".
来源：https://stackoverflow.com/questions/46448943/how-to-remove-device-from-apple-developer-account-while-resetting-device-list