The correct inference is that the saltwater solution is hypertonic compared to the cell.
When a cell shrivels up in a solution, it indicates that water is moving out of the cell into the surrounding solution, which happens when the solution has a higher concentration of solutes (like salt) than the inside of the cell. This higher concentration of solutes in the solution causes the cell to lose water and shrink, hence the solution is hypertonic compared to the cell.