Tire engineer here.
The link didn't actually say HOW to use the chart. I suspect what you are supposed to do is if you fill your tires at a certain ambient temperature, use the chart to tell you how much to fill it to. That way at 70°F, you will have the proper pressure.
Alternatively, if you are filling your tires at 70°F, then use the chart to make sure you have enough tire pressure when it gets down to the temperature indicated.
Either way, I think this creates more confusion than is needed.
So there is a bit of wrong information on the page. For every 10°F change in ambient temperature, the pressure inside a passenger car tire changes about 1 psi. For other tires, use 3% for every 10°F. (Note: 3% of 30 psi is about 1 psi)
Please note that the tire manufacturers want you to inflate your tires to the vehicle manufacturer's specified pressure for whatever the operating conditions are. That means that if you are operating at 10°F, they want you to use the specified pressure, not one specified for another temperature. That also means if you fill your tires at 70°F, then they will be too low at 10°F (about 6 psi low).
Yes. yes, it is confusing.
Now allow me to express my opinion: Winter tires would benefit from a few extra psi. (3 to 5 psi) That extra pressure helps push the footprint through the snow to reach the pavement. The pavement will always have better traction than snow.
Some people will argue that over inflating your tires will cause the center of the tread to wear faster that the shoulders. That is true, BUT that effect is small compared to most other things that cause rapid wear, such as alignment and the drive vs steering effect.
Drive vs steering effect? Steering tires tend to wear the shoulders and drive tires tend to wear the center. You can see this clearly on a RWD car - where the wear rates are about the same front to rear but in different portions of the tread. That's why rotating tires gets you longer tread life.
On a FWD car, you can't see the steering vs drive difference as the front tires are doing both - BUT - that also means that the front tires are going to wear more rapidly that the rears. I've measured about 2 1/2 times faster. Again rotating tires helps even out the wear.