background复合属性这段代码怎么理解,谢谢.

Question

 background: linear-gradient(white, white) padding-box,
 repeating-linear-gradient(-45deg,red 0, red 12.5%,
                                      transparent 0, transparent 25%,
                                      #58a 0, #58a 37.5%,
                                      transparent 0, transparent 50%)
                                      0 / 5em 5em;  最后的0代表什么意思？谢谢