Does anyone know if the SSDI offset applies to amounts exceeding 80% of your former gross income, or former net income?

My weekly workers comp settlement amount, combined with my SSDI benefit, will exceed 80% of my former net monthly income (I'm basing that on the best month out of the last five years I worked).

But it will be under 80% of the gross amount.

Does anyone know if the 80% refers to the net or gross amount?

I'm in California.

Any help would be appreciated. Thanks.