Warrior's experience is relative to his level.
Warrior starts with 100 epx and level 1.
Then collects 300 exp total, warrior now is level 3.
Then collects 400 exp total, warrior now is level 4.
Level 9 warrior should have 900 exp or more up to 1000.
Up until level 10, warrior's rank is 'Pushover'. From level 10 to 19 'Novice.'
What do you mean by '300 should equal 400'?

A number can't start with 0, 1 to 4 are already there, so the lowest possible digit is 5.