Draw out a number line. Make sure -28 is on the number line, along with other optional values (such as 0 perhaps). At -28, plot an open circle or hole. This indicates this value is not part of the solution set. This is because there is no "or equal to" as part of the inequality sign. Then shade to the left to indicate values smaller than -28.
So in summary, you'll have an open hole at -28 and shading to the left.