I don't understand your problematic.
Points are integers.
If you want a maximum point of 1 per order, then it means you can only have either 0 or 1.
So above a certain amount, you want 1 point attributed to the customer. Is that all the time ?
And below that, should it be 0 points ? For everyone ?
If you want 1 point attributed per order all the time for everyone, then you can just enter 1 in the "registered" user group point and 1 point will be given per order to all the registered users purchasing.
But I suppose it's something else you want but I didn't understand what you want exactly.