When you run numerator(lfparc[4]) the calculator is treating lfparc[4] as an unsimplified symbolic expression instead of a clean numeric value, so it returns a symbolic expansion of the numerator... causing the result you saw originally. I suspect the manual input works because the computation bypasses symbolic complexity. As an untested hypothesis, we might be able to get around this issue using simplify() before numerator() to avoid the issue we are seeing with symbolic expansion. I'm not very well versed with the fx-CG500 so I hope this response will help you as you investigate future computations.
When you run numerator(lfparc[4]) the calculator is treating lfparc[4] as an unsimplified symbolic expression instead of a clean numeric value, so it returns a symbolic expansion of the numerator... causing the result you saw originally. I suspect the manual input works because the computation bypasses symbolic complexity. As an untested hypothesis, we might be able to get around this issue using simplify() before numerator() to avoid the issue we are seeing with symbolic expansion. I'm not very well versed with the fx-CG500 so I hope this response will help you as you investigate future computations.