The box of pasta shells I got contained 36 shells. Cook the entire box because some shells may be broken or may break during boiling.
Make sure to use at least 1 ½ cup salsa otherwise it will be too dry. If it is too spicy, you can use just 1 cup of salsa and add an extra ½ cup water.
Make sure to use lean ground beef otherwise the pasta will be too greasy. If you purchased a fattier package of meat, you can scoop the excess grease out or use a paper towel to help soak some of it up.