I would like to extrude the two shapes, which are separated by this spline line. But when I extrude, I see that there is a gap between the two shapes. When I click on the sketch, there is only 1 spline line. Where is this extra white gap coming from and how can I get rid of it so my shapes can extrude properly?
That might be artifact from zooming in so close.
Your are at .0005CM grid level.
View it in visualization and it will likely be gone unless it’s in the sketch.
Low poly representation in the modeling mode IIRC.