_ScreenLogStruct_.Items (first field) is pointer to array of _ScreenLogStructItem_, the first one starts from _ScreenLogStruct_.FirstItemShift index. It's a circular buffer.
_ScreenLogStructItem_ has field ShowTime (int32, time in milliseconds, when item was shown the first time.

There is also global ScreenLogStruct variable in IDA Pro. Probably you can use IF:L + locate the last item in circular buffer and adjust it's show time (timeGetTime() - 10000).