They were advice is to use lotion with the highest sun protection factor. SPF, possible.

他们建议使用防晒系数最高的乳液。防晒指数，成为可能。

It stands for sun protection factor, and based on that name, it seems like it should tell you how well you'll be protected from the sun.

它代表防晒指数，这个名字好像是告诉你产品的防晒效果如何。