What does "Systematic" or "Extensive" processing mean?

The GDPR does not define the terms “Systematic” or “extensive” processing but the concepts should be understood in relation to the following: 

• When processing occurs according to a system
• When it is pre-arranged, organised or methodical
• When it occurs as part of a general plan for data collection
• When it is carried out as part of a strategy
• When it implies that the processing covers a large are or involves a large range of data or data subjects