Hi,

The punishment value is calculated based on the configuration parameter 40, which specifies some related values, including:

• default_flat_fine
• default_proportional_fine
• severity_flat_mult
• severity_proportional_mult
• long_flat_mult
• long_proportional_mult

If this configuration parameter is not specified, then the maximum punishment is 101 TON, otherwise it's calculated as below:

let: flat = default_flat_fine * (severity_flat_mult / 256) * (long_flat_mult / 256)
let: part = default_proportional_fine * (severity_proportional_mult / 256) * (long_proportional_mult / 256)
then: max = flat + (part * stake / 4G)
while: 4G = 4 * 1024 * 1024 * 1024 = 4,294,967,296

Finally, max-punishment = min(stake, max)

At the moment of writing this answer, the config parameter 40 is empty, so the maximum punishment value is simply 101 TON.

If you want to check the code, see pool.fc line 84.