Why is the B737 altitude display unneccessarily ambiguous? I was playing FSX again lately and was flying the B737-400. So I hope it is simulated correctly and this question isn't dead on arrival :-)

It always bugged me, that the altitude display on the MFD is very ambiguous when you are immediately below a "round" value:



On first glance everyone (ok..me) would read the altitude to be 9900 ft. Only if you know what to look for and spot that the numbers carry on downwards you can deduce that you are actually at 10000. The reason is that the second significant digit does not roll over smoothly but ticks over appruptly when the next round value is surpassed.

Granted, 100 ft may not be a huge difference, but it seems very unneccessary to have it like that. If the first two significant digits behaved more smoothly without this round-down like behavior I would recon that it would be way less ambiguous.

Why is the altitude display designed that way?

Edit: Here is what it looks like in motion:
Because thats how old school "steam" altimeters work/look and glass cockpits were designed to work similarly such to reduce unfamiliarity when transitioning. Prior to the screen age a drum altimeter would have read out and increased in much the same way the glass cockpit does now. 



(source)

You will also notice the 10's and 1's place's are joined and rounded off by 20's. This has to do with the common arrangement of tick marks on any old altimeter as well as the fact that in a fast climb the one's digit would be unreadable. 

On any note, its not ambiguous to a pilot, its actually quite accurate if you know what you are looking at.