Displayed values are stretched (i.e. duplicated over time interval where no time series exist)

Hello,

I’m new to Grafana and maybe I do something basic very wrong but I tried many things including googling to no avail.

My problem is that displayed values are stretched (i.e. duplicated over time interval where no time series exist). While I have data samples taken only once in 4 hours here is the graph that I get using bars:

And I expect to see something like this (see the red bars):

The same with points:

And I would like to have this (see red points):

How can I achieve this?
Thank you!