Set accurately Assets in Xcode 7 for all iPhone devices

I am looking for best solution for setting image assets in Xcode 7, I googled and found many threads those are discussing on setting on image assets. Here below is what I found

• 1x images are for the original iPhone through the 3GS - 'standard' resolution devices (3.5" screens)
• 2x images are for the iPhone 4 and 4S (3.5" Retina screens) and are
  also used for the iPhone 6.
• Retina 4 2x are for the iPhone 5 and 5s (4" Retina screens)
• 3x images are for the new iPhone 6+ (5.5" super-Retina [3x] screen)

as also shown in attached image.

But there is no more Retina-4 option so I am confuse how to set accurately in below attached image.

1x: is for non retina

2x: is for retina (confuse here either for iPhone 4 Retina, 5 Retina or 6)

3x: is for 6 plus.

Correct me if I am wrong. Looking for clarification. Thanks

You will get all the information regarding Asset from top to bottom on this link.

About Asset Catalogs

According to your Question you can find information in proper detail on this link iosdesign-guidelines

Developers work with point values, so it is important to understand the difference with pixels. When the iPhone was first introduced, the two units were the same: 1pt equals 1px. Then when retina screens came along, 1pt became 2px. So think of points as the values in the original iPhone, and pixels as the real values depending on the pixel density (iPhone 4,5,6 = @2x, iPhone 6 Plus = @3x).

Check here for resolution ultimate-guide-to-iphone-resolutions