John from PA wrote in post #18859515
I checked my 60D and can’t find a 4-digit counter on the rear screen. I also have an 80D currently on loan to a family member with new baby so perhaps that will display the needed info per “cristphoto” mentioning “newer” bodies.
The card being used is a Sandisk Extreme SDXC 64 GB 90 MB/s. Note there is a newer version with a higher speed but at $10 per card these are ample for my needs.
Thanks, John.
Interesting. 
So, I fire up my 50D.
Top LCD indicates around 103 shots left on a CF card.
Rear display also shows an estimated 103 shots left of 2.41GB free, on an 8GB card.
Reading the card on my PC, I see there are 5.2GB used(I'll have to cull that!),
with 2.41GB free. It seems Canon reads the card like Windows does.
Inserting an empty 16GB card tells me I have 647 images' worth of storage.
My camera is set to record RAW only; I'm sure it makes a difference.
Checking further, I see in recording options:
RAW=15M=647
SRAW1=7.1M=999
SRAW2=3.8M=999
So, you are correct, at least as to the older cameras.
My 50D's counter only seems to apply 999 as a maximum estimate for high-capacity cards,
even though it can use the entire available capacity of CF.
The behavior may be different for SD cards, although I do not know and can not verify.
This is an interesting lesson to me, albeit inconsequential to my use.
I'm not much concerned with accuracy of the displayed count, with several cards
at my disposal up to 64GB. I just swap the card on the very rare occasion my camera
reports low capacity remaining.
Still, it may be of some genuine interest to those with limited cards on hand.