Example:
Craft Firebowl cauldron.
Needs: 50 iron, 20 twine.
Inventory has 50 iron and 19 Twine.
When you have 19 twine the icon in the craft requirements section of cauldron will be DIMMED. (>Go make twine)
When you have 20 it will be LIT. (>go craft caldron)
Suggestion: Click ( dimmed) icon to go to the relevant icon in the craft menu, in this example the twine icon.