The number moves while you build.
You split €20,000 across four categories: Carpenter, Materials, Appliances and IKEA kitchen. The app counts each one down as the expenses land, and says what is left to allocate. Right now €0.
The carpenter has taken €3,980 of his €4,000, materials €3,720 of €4,000. The kitchen as a whole sits at 90%, and that is a number you see before the next order rather than after it.