Hi Susan. Graphs are diagrams, not tables, even though the narrative calls it a table.
In the first graph, as you said, M T W Th F are abbreviations. Use the ELI for M T W F; don't contract Th.
In the second graph (trail points), although the points would use no ELI in the actual drawing (not shown), they are single letters here (as axis labels) just as they would be in narrative. Use an ELI for each letter.
Note that if either graph showed labels next to the actual *points within the graph grid, that would qualify as a labeled diagram and you would not use an ELI for those capital single letters.