I agree the number with CDiddy, actually the safety result should sound even better and can be summarized by
"Leronlimab lower patients with SAE by 58% comparing to Placebo"

My calculation is as below:

SAE Total
Leronlimab 5 56
Placebo 6 28

SAE - meaning number of patient with SAE

Since "Total" in Leronlimab and Placebo are not the same, we need to scale the numbers in Placebo so that both "Total" are the same then we can use the SAE column to calculate the correct percentage.

After multiply result for Placebo by 2, we have the following:

SAE Total
Leronlimab 5 56
Placebo 12 56

Now, with the "Total" the same for both Leronlimab and Placebo, we can find the percentage lower of Leronlimab versus Placebo

Percentage lower of patient with SAE = 100%* (12-5)/12 = 58%