I think the point of the workout is to do the same amount of reps (30) with 10x3 as opposed to 3x10 right? The point being that you are using more overall poundage during the workout. So going off of a 1 rep max of 305, you could potentially do 10 reps with 75% of that which is about 228. So you'd be doing 2280 pounds total for each set and 6840 for the whole workout.
If you use 85% of your one rep max for 10x3 you'd be lifting about 2600 pounds for each set and after 10 sets you will have lifted a grand total of 7800 pounds for that workout. If you need to lower it in order for you to accomplish the set amount of reps to say 80% of your 1 rep max, you'd still be lifting 7320 pounds per workout which is 480 more total poundage than if you'd done a traditional 3x10. So even if you have to lower the weight a little bit more you're still going to benefit from this workout. Unless of course you are unable to use more than 75% of your 1 rep max for 10x3.