How does the 10th-level spell slot FAQ interact with everything?

5e spell slots-APK-IN V spell slot Spell slots represent the caster's mental limits D&D 5th edition's Player's Handbook, p 201, under Spell Slots, describes them thusly: spellbinding mystery slot You cannot cast Counterspell using a 1st or 2nd level spell slot, because it's a 3rd level spell What it's talking about is the spell you are *countering * In

spell slot counter To cast one of your warlock spells of 1st level or higher, you must expend a spell slot You regain all expended Pact Magic spell slots when you finish a short