The concept of a line assists the person to follow a sample stored in their working memory for a few seconds. They can use two striking features at a time as this enters the scale in ACL 4.4. This increases their speed and accuracy. The difference between ACL 4.6 and 4.8 is the person's ability to stick to checking with the sample. At ACL 4.8, the person can check with the sample until they are done. At ACL 4.6, they may get side track and stop matching to the sample as their mental energy is exhausted.