-1 level???

Well.. to begin, I was in a tournement with 8 players and I won. the next round I won again and I just needed 127 exp and i got EXACTLY 127 exp... so it said i leveled up, but when it said what i got (weapon) it glitched out and i went to the next match (finals). then i lost and i saw that i lost 1 level? (lvl 59)

 

well i never had this problem in ssl steam,I had once in ssl2 that i lost 5 lvls(at lvl 45/50 xD) but it happened only once and not even in ssl steam but the previous one.Can you explain me what means -1?that means you had to do ALL the lvl again?