Then, count by twenty, for the beginning and to the end !
Numbers are one of the stuff I hate in danish, and my danes friends agree with me (saying it is utterly absurd : reverse in the middle of the number : hundred -> units -> tens, and counting in twenties from 50 -> 90... wtf)!
It is like walking half the way straight and then suddenly deciding to go backwards the rest of the way... WTF ?
counting with a 12 base was for 10 fingers and 2 feet... hence feet having 12 inches and the old shilling being 12 pence etc (also apparently the reason why 13 was a taboo... people couldn't count after 12 and everything after was unknown and therefore to be feared.) twenty base counting apparently started after using 10 toes and fingers together. ( think that reference is dubious though.... ) but it helped me to accept counting with a 20 base.