The 1st 3 digit number is the width of the tire in millimeters (the larger the number the wider the tire), the second 2 digit number is the sidewall height as a percentage of the width (1st number) (larger mean taller sidewall) and the last number is the rim/wheel diameter in inches. This is probably the only product that combines metric with standard with a inert (%) all in the same size spec.The first set of numbers is Width. 2nd is Aspect Ratio (% of Width). 3rd is Rim Size.
195/55/15 is 1 cm narrower. And Slightly smaller Sidewall height.
The problem I see is, The TPMS. Unless your reusing the factory rims, You need the sensors and have the car programmed. Then do the same(Reprogram) when you change to "Summer" tires.
On a Side note, The Stock Tires 205/55/16 Suck in snow. The Hankooks on the Malibu (Factory) were better. 205/45/17 (If I remember correctly)