There are something wrong about the Avg generation time in my database

As the pictrues show, the parameter “custom_float” were obtained by the parameters “gt_ms”.I know that the parameters “gt_ms” was calculated from “performanceAlias.timing.responseEnd - performanceAlias.timing.requestStart”, rewrite from “window.performance.timing.responseEnd - window.performance.timing.requestStart”.But how could it be? “window.performance.timing.responseEnd - window.performance.timing.requestStart = 154321000000” is impossible.I don’t have any idea for that.Does anybody know why that is? Can you help me, thanks?

Only thing I can think of is somebody having a broken browser (or maybe a browser extension) that makes one of those two calls to return somthing invalid.

Now I know that this problem would only happen in the Safari 10 or 9 of IOS.But I still don’t know why.Maybe you and you teammate can find a way to solve it in the next version.If you know something about that, please tell me!