how make level digimon not stop in level 14,15 and 18?

Every digimon has a level limit. It is decipited with a
Whole ton of 9s on your digimon's exp needed to get to the
Next level. So when you see this, even when you fight more
Battles, the exp values will not decrease. To get a higher
Level limit, you have to DNA Digivolve! And only digimon
Who are at Champion Level or higher can DNA Digivolve.

A recurited digimon's level limit will always be the same.
It will only change when you recurit a higher level Digi.
There is no formula for calculating this (I couldn't
Find it anyway. This applies to traded digimon too. But I've
Somehow bumped into some exceptional cases...

When you DNA Digivolve, your digi's EL limit will increase.
There is actually a formula for calculating this. Someone
Gave me the actual formula. (Thanks [email protected])
I've tried it a few times and it works. (Better than mine anyway)

Digimon1(highest level) digimon 2's level divided by 5(round down)

Example:greymon lv 15 airdramon lv 13
Add 15 to 13/5...13/5 equals 2
15 2=17,your new digimon's max level.

Steps Explanation
1. Take the ELs of the 2 digimon that you want to DNA Digivolve
2. Take the digimon with the lower EL and divide by 5(If it's the
same, just take anyone of them)
3. Round down the result to the nearest whole number
4. Add the result to the digimon with the higher EL
5. The end result is the EL limit of your new digimon

Info from http://www.gamefaqs.com/ps/437339-digimon-w..