I added a helper column and just kept the right-most 15 characters, and the countif worked, not sure if this is something the OP would consider....
G
H
I
2
 169214000798449
3
 169214000798381
1
4
 169214000798384
1
5
 169214000798344
1
6
 169214000798444
1
7
 169214000794444
1
8
 169214000744444
1
9
 169214000744444
2

G2=TRIM(RIGHT(A2,15))
I3=COUNTIF(G$2:G3,G3)
both copied down

The 1st 4 digits seems constant