The writer is attempting to understand the selection process that results in a merged list using the bestPi algorithm, which is referenced via a link. The challenge lies in comprehending how the original list L1, represented as [5,3,1,8,0], transitions into a set of chunk feerates labeled [5, 4, 0].

To clarify, the bestPi algorithm selects a common element from both lists, in this case, $L2 \cap [5]$, which is the number 5, to initiate the sequence. This results in a merged list of [5,8,3,1,0]. However, when the writer computes and compares the potential $C_1$ and $C_2$ (which are not explicitly defined in the context but imply some form of calculation or subsets), they end up with a different merged list: [8,5,3,1,0].

The confusion arises with the chunk feerates, where it is unclear how the list [5,3,1,8,0] can be broken down into the chunks [5, 4, 0]. The concept of chunks here refers to portions or segments of the list that are identified by specific criteria, likely related to their values or positions within the list. The writer expresses difficulty in visualizing this transformation and seeks clarification on the definition and determination of these chunks within the context of list manipulation and the bestPi algorithm.