Answer
This is an intentional, by-design limit built into most Lobby element types, not a configurable setting — it exists specifically to prevent performance and rendering issues, since Lobby elements are meant to give a high-level overview rather than render a large full dataset. If a genuinely large dataset needs to be fully displayed (rather than summarized), use a List element instead of a Line Graph — List elements are better suited to showing larger row counts than chart-based elements like Line Graphs.