Ranked versus Practice
From Warzone Wiki
Your public profile displays information about any ranked games you play in. It will simply display wins and losses of finished ranked games.
Practice games don't effect the win/loss percentages on your profile. Practice games are ideal for new players or for testing new game settings.
One should not put too much emphasis on the ranked game statistics, as they are trivial to manipulate. For a much better measure of how skilled a player is, check their Ladder rank.