If you get an amount of EXP that would level you up twice or more, you will level-up once and be at 99.99%. In the old source, getting any extra EXP would level you up again and you would get the remaining EXP in the next level, but in the new source, all remaining EXP is lost.
tbh 1 level + 99.98% was how it originally was in gms, but not too sure if it was intended in this new source.