168.0 C sparge water sure looks that ought to be Fahrenheit.
For BIAB in a 15g pot you shouldn't be sparging separately. There are some checkboxes and options that you must have selected wrong. For your equipment, the best match IMO is the one that says "Pot (13 gal/50 L) - BIAB". You actually have a bit more space in the pot, but for most recipes, this preconfigured setting will work well for your setup. Also when you set up the mash, there is a specific configuration that you need to choose which for a Saison would be "BIAB, Light Body". This will get you somewhat in the ballpark, but still not correct in my experience. What I mean is, you will have all the water in to start with, but as I will explain below, the recipe steps it shows do not really have the right numbers or descriptions of the process.
First off--I will say that I do NOT generally trust Beersmith's numbers and instructions for BIAB in the recipe steps, because the instructions are written to work for a traditional mashing process, and I don't think he changed them for BIAB to read appropriately. In particular it has very strange numbers for the volumes of water to add, and also I think the temperature of the strike water is wrong still--it seems like it uses a strike water temp assuming a much lower volume than what it should. He MAY have fixed this since the last time I checked it, although I want to say that although he fixed the temperature issue, the volume was still wrong in the instructions.
I wrote my own calculator for the volumes, and for the temperature I generally just heat my strike water to about 2 degrees F above my intended mash temperature before doughing in.
Here is a link to my calculator
. Please keep in mind that if you plan to use it, you may want to use google docs to make your own copy of it, as other people use it and the numbers may change on you as you're trying to play with it.
The steps for doing BIAB should be straightforward:
1. Use the calculator to find the "Water Volume Needed" for your batch.
2. Fill your pot up to that level with your treated (if necessary) water, and start heating it up to your intended strike temp. As I said before, my strike temp is usually about 2 degrees F above my intended mash temperature. If you are doing direct-fired BIAB, it is easy to heat up your mash a bit if you are a bit low, but going too high by more than a degree or two can be a pain in the butt.
3. Stir in your grain. Typically I add about 1/2, stir, then add the other half and stir again. When you are mashing with the full water volume you don't have to worry as much about doughballs as you do with a cooler MLT setup, although you still want to stir everything thoroughly.
4. Check my mash temp. Usually I am right on target, but if I am a bit low, I will turn on the burner and heat while stirring, and the temp will usually get there very quickly. For a saison in particular, unless you are VERY low there's probably no good reason to worry about it. Low mash temps are better for the style, anyway. If I am a bit high, I will continue stirring (no heat, naturally) until the temperature comes down.
5. Cover up the pot and let it sit. If you have facilities to recirculate, this would be the time to get that going.
6. When the mash is done, pull the bag out and let it drain/squeeze/etc. to get the wort out. I will do an initial squeeze, then put it in a bucket and tie the bag to a door handle or bar on my brew stand to let it hang over the bucket and continue draining.
7. Turn on the burner to start heating the wort to a boil.
8. When the wort is getting close to boiling, take the runnings from the bucket, and add them back into the pot.
9. Continue your batch just like every other beer. During the boil I will usually clean out my bag and hose it off, before hanging it to dry. I will then toss it in with the rest of my laundry before my next batch.