I used 4 cups mashed berries - strawberries, marionberries, blackberries and two cups sugar.
I added 1 cup red currant juice since I had some on hand and 2/3 cups apple pectin.
It is still delicious and sets well enough on a english muffin but would slide out the sandwich if I took it to the edges.
In all I think I cooked it 15 minutes or so and should have taken it a bit longer. But I have also found that cane berry jams will look very different in the pan then strawberries. I haven't made blueberry jam yet this year but I suppose that will look different to. And what I mean by that is there is a difference in texture, thickness and overall consistency when judging when it is ready to come off the stove.
Since I do not use thermometers I am dependent on smell and appearance. Strawberry jam alone seems to need a cooking that "parts the waters". By that phrase I mean I usually cook the jam until I can take my spoon across the bottom of my pan and see the bottom of the pot for a second before the jam flows over it again. I do not do that when using cane berries and certainly not when I have added currant juice to the mix. This has something to do with the natural pectin amount in the fruits and, I suppose, cellular structure of the different fruits.
When using cane berries I stop before the "parting of the seas" since that would be too long for my liking. I stop just before then. But then you will understand all this once you get in there and start making it. You just have to do it yourself and experience the variances. That is the one thing about making jam without pectin in the box. You will have to learn by doing. The formula on the instructions in the pectin box is "foolproof" but also requires lots of sugar - much more then you will like and certainly takes out all the skill, quality and personal creativity out of the effort.
In the end, if I want to set my jam a little more I can unseal it and put it back in the pan, bring it back to the boil (I can do this cause I am using natural pectin - you can't with the boxed stuff) and cook it another minute before sealing again. That is totally doable. But I'm happy and think I will get some loganberries and more marion berries and see what I can do.
And remember, you can make jam with frozen berries too so if you don't have the time or inclination to make jam with your fresh berries. Just stow them away for a while and make it when the kitchen and seasons have turned cool again. The smell of jam making on a cool winter's morning ain't half bad. Just thaw the berries before you start and then follow the basic formula - 4 cups berries or juice. Two to three cups sugar. 2/3 cups apple pectin (cooked with the fruit for a minute or so before adding the sugar to the pot) and a little lemon juice if your berries need an acid punch (you can tell this by taste - acid helps in the gelling) and cook once it is at a full boil for anywhere from 12 to 20 minutes depending on your berries, pan and heat source.