It's all been said, but not explained.
When crafting with residue the residue used is added to the TT of a successful result.
If you were to craft and the result is worth 5 peds with a max TT of 100, that is not a glow. This is clear, and understood.
Next click you make an item worth 95 peds, that is a glow. Also clear and understood.
Add in residue TT=200 peds and make the above 2 crafting attempts again: (imaginary)
First click and you will get the item worth 100 peds, and use up 95 peds of the residue, and have 105 peds of residue left. This is not a glow, as you only made an item worth 5 peds: you used the residue to make the item up to full TT.
Second click you get a 95 ped glow and an item worth 100 peds. You have 100 peds of residue left. you made an item worth 95 peds, and used 5 peds of residue to top the value of it up. This is a glow, you made an item worth 95 peds.