Taking an unaugmented human that represents a world-class athlete aka the pinnacle of human achievement, use Body 6 and Strength 6 for a total dice pool of 12. Using mathematical average, minimum, and maximum, this yields the following results.
20kg * STR, 5kg/hit
Min: 120 + 5 = 125kg
Avg: 120 + 20 = 140kg
Max: 120 + 60 = 180kg
20kg * STR, 10kg/hit
Min: 120 + 10 = 130kg
Avg: 120 + 40 = 160kg
Max: 120 + 120 = 240kg
40kg * STR, 10kg/hit
Min: 240 + 10 = 250kg
Avg: 240 + 40 = 280kg
Max: 240 + 120 = 360kg
40kg * STR, 20kg/hit
Min: 240 + 20 = 280kg
Avg: 240 + 80 = 320kg
Max: 240 + 240 = 480kg
The current world record is around 260kg in a clean & jerk move. To my mind, then, none of the above really hit this mark as this is supposed to be the absolute maximum an unaugmented human could possibly lift. 20kg * STR with 10kg/hit comes close, but you'd need 12 hits to get there which with a dice pool of 12 is just plain unrealistic. Let's therefore look at some other options.
25kg * STR, 15kg/hit
Min: 150 + 15 = 165kg
Avg: 150 + 60 = 210kg
Max: 150 + 180 = 330kg
On a good roll (8 hits on 12 dice), the above would allow one of the strongest unagmented people in the world clean lift 270kg, just over the current world record. On an exceptional roll (i.e. using Edge, for example, and getting 10+ hits), this would go up to 300+ kg. To my mind, this is a good approximation of real world capabilities.
Let's take this approach and apply it to a human of average strength and a troll of superb strength, as well as the absolute maximum a troll could achieve.
Average Human, Body 3, Strength 3
25kg * STR, 15kg/hit
Min: 75 + 15 = 90kg
Avg: 75 + 30 = 105kg
Max: 75 + 90 = 165kg
Superhuman Troll, Body 10, Strength 10
25kg * STR, 15kg/hit
Min: 250 + 15 = 265kg
Avg: 250 + 90 = 340kg
Max: 250 + 300 = 550kg
Superhuman Troll, augmented and/or magically enhanced, Body 15, Strength 15
25kg * STR, 15kg/hit
Min: 375 + 15 = 390kg
Avg: 375 + 150 = 525kg
Max: 375 + 450 = 825kg
Those are your ranges for what is possible, but the latter categories are always going to be near-unattainable simply because rolling 100% hits is going to be challenging the bigger the dice pool becomes, even with Edge. I personally feel these numbers are realistic enough that I'd be happy to replace them with the book values, which I agree are odd. So to answer your question, I would go for 25kg * STR, plus 15kg per hit.