To qualify for Supplemental Social Security Income benefits, you must meet income requirements. One of those is showing you do not have substantial gainful activity.
The Social Security Administration explains that substantial gainful activity is a threshold for work and earning.
SGA requires significant mental and/or physical capabilities. It will be work for which you receive some type of compensation or that would normally earn a person compensation, even if you receive none. In general, you can consider SGA a guideline for how low your earnings need to be to receive SSI benefits.
The SGA limit for 2020 was $1,260 or more per month. If you earned under that, then you will meet the requirement for not have enough income from substantial gainful activity. The SSA does not require that you work full time to meet the SGA. You can work a part- time job if that is the only employment you can get or all you can physically or mentally handle working. Working part-time should not count against you in most cases as long as you meet the other requirements for SSI.
The SSA will change the limit if the cost-of-living changes. Changes occur every year in December, and follows a set formula for determining the income based on the COL change.
If you are blind and seeking SSI, you have different guidelines that non-blind individuals. You do not have to meet SGA requirements. Note that this is only for SSI, it does not apply to other Social Security benefits for which you may apply.