This is how Warlock Spell Slots work!

You're Playing Warlock WRONG in D&D 5e?! warlock spell slot table Use this total to determine your spell slots by consulting the Multiclass Spellcaster Slots PHB Page 107, Warlock, Pact Magic, warlock spell slot table Warlocks do not cast spells through the Spellcasting feature, but through their unique Pact Magic feature Spell slots granted by Pact Magic are

warlocks book slot The Warlock table shows how many spell slots you have The table also shows To cast one of your warlock spells of 1st level or higher, you must expend a spell