1 files changed, 4 insertions, 1 deletions
diff --git a/styles.go b/styles.go
index e4f3a27..0ae9e51 100644
--- a/styles.go
+++ b/styles.go
@@ -930,7 +930,7 @@ func formatToE(v string, format string) string {
 	if err != nil {
 		return v
 	}
-	return fmt.Sprintf("%.e", f)
+	return fmt.Sprintf("%.2E", f)
 }
 
 // parseTime provides a function to returns a string parsed using time.Time.
@@ -1115,6 +1115,9 @@ func parseFormatStyleSet(style interface{}) (*Style, error) {
 			return &fs, ErrFontSize
 		}
 	}
+	if fs.CustomNumFmt != nil && len(*fs.CustomNumFmt) == 0 {
+		err = ErrCustomNumFmt
+	}
 	return &fs, err
 }