One interesting thing I discovered recently is:
I have a graph with several items: all configured for 30d history and 3650d trends. But one item (zabbix trapper) configured for 3650d history and 0d trends.

I open the graph with 7 days period and:

• when the trapper item is very last in included items list - in right bottom corner i see "Data from history ...". But that's not truth as actually most of items on the graph are from trends.
• when very last item in included items list has trends - in right bottom corner i see "Data from trends ..." Again it's not truth.

Attached graphs show that.

It's suggested in such cases use "Data from history and trends .." in the graph corner.