The value of the XpTotal tag of a player which is used as value for scoreboard objectives of the criteria type xp and the query result of the /xp command when giving experience (not levels) does not account for level changes.
It is basically the number of experience the player has collected. It only resets to 0 when the player would have a negative experience level.
- Create a scoreboard objective tracking the xp of a player
- Use for example the /xp command
Based on 1.11.2 decompiled using MCP 9.35 rc1
The tag XpTotal (field net.minecraft.entity.player.EntityPlayer.experienceTotal) is only increased by the method net.minecraft.entity.player.EntityPlayer.addExperience(int) and additionally never decreased.