Self-consumption is the percentage of energy you use of your own production.
The formula for Self-consumption is (Total production - Export) / Total production.
Example in the screen below: (592 - 241) / 592 = 59%
Self-sufficiency is the percentage of used energy covered by your own production.
The formula for the Self-sufficiency is (Total consumption - Import) / Total consumption.
Example in the screen below: (382 - 31.4) / 382 = 92%
Please note this calculation only applies to configurations where "only surplus" is selected as a solar production configuration. If you select "export all" as a configuration setting, you are telling the system that you immediately export all solar production to the energy supplier and are using none of it for self-consumption.