Right, maybe I should add a little bit of a "how to". I thought it was pretty clear, but it can never hurt.
I'm gonna use a couple of screenshots as an example.
Let's assume we have a digimon that is lv 75 and you want to level it up to lv 80 (so you can limit break it once more). We have queen rarity food ready to go.
So we set the "level start" to 75, then we set the "level goal" to 80. And the rarity we set to queen.
The result is "You need:
2 fuse(s) using 5 Queen rarity digimon at level 27"
So we need to get 10 queen rarity digimon at lv 27 and fuse those into our target digimon.
We want to level the same digimon and again we have queen rarity digimon ready to go. However this time we don't wanna level them up higher than lv 15 (since feeding a queen rarity with 5 queen rarities gets it to lv 15). So we set the "food max level" to 15.
The result is: "You need:
3 fuse(s) using 5 Queen rarity digimon at level 15"
So we'd need to get 15 queen rarity digimon at level 15 and fuse those into our target digimon.
Same situation as example 2, however this time we're gonna assume we have an unlimited amount of gold floppies. So we set the "use item" enabled and set the item that is used to floppy gold.
The result is: "You need:
2 fuse(s) using floppy gold and 4 Queen rarity digimon at level 1"
So all we need is 8 queen rarity digimon at level 1 and 2 gold floppies and fuse those into our target digimon.
We noticed in the last fuse that there was a bit of an overshoot. So instead of using unlimited gold floppies we only want to use one. So we set the "max amount to use" to one.
Now the result is: "1 fuse(s) using floppy gold and 4 Queen rarity digimon at level 15
1 fuse(s) using 5 Queen rarity digimon at level 13"
So we need to do 2 fuses both with differently leveled food and one with a floppy gold.
NOTE: Keep in mind that doing the fuse that gives the least amount of exp first (so the one that doesn't use the gold floppy) costs less bits.
Same as example 4. This time we want to use a silver floppy in the second fuse. So we set "use item" for "second item" enabled and set it to floppy silver.
This time the digimon in the second fuse need to be a lower level.
Same as example 5. The only difference is that this time the target digimon is dragon race. Floppies are of dragon race, so the item is of the same race as the target. Set "item is same race as target" enabled for every floppy that is used.
This is the result.
I hope this explanation is good enough. If there are further questions let me know.
The only thing I didn't mention is that it's also possible to limit the amount of secondary items used and in that case a third line is also shown that uses no items.