Here is a step by step breakdown of the five metrics:
This is the most important factor in calculating your grade as it is worth twice as much as the others. This mainly depends on two key factors- Your survival time, and how many people die around you, if you dont kill them(Like landing in Pochinki)
This is the most obvious one as it depends on your kills. This depends on- Your total kills and your K/D ratio
This is self explanatory, damage depends on the Damage count(you got 325)
In solo mode this depends only on Health recovered so you could intentionally damage yourself and heal to get this rating up.
In team mode this depends on two factors - Health recovered and Reviving teammates
Supplies depends on how rare the items are which you pick up during the course of the game. So say a Kar98k would get you more Supplies points then a UZI. Also drop guns are worth more than their non drop counterparts.
At the end of this, your total rating is calculated by taking an average with 2x weightage for Survival, as mentioned.
I suppose the grade is then calculated the same way as school grades are, say SSS for 95+ rating(not exact figures).