Thank both of you.
It is true, the solution is to change the attribute "point":
<ma-point-values point="point1"
by the attribute "point-xid" with the XID of the data point you want to draw:
<ma-point-values point-xid="myXID"
Could be a good idea to add an example to the "Mango Dashboard Examples" with this option to draw a chart.
Thanks.