How do the numbers on photos work ?

[AC Question]

My girlfriend sent me some photos tonight and the photo number were consecutive, about an hour later she sent me another and the number was nearly one hundred higher, does this mean she had taken another 100 photos in between the photos she sent me ?

 

[Tim1954]

Perhaps they are taken on a different camera...

 

[ManiacJoe]

Depending on the naming convention used, the file names often contain a date and a time and a sequence number.
Look at the file names and figure out which digits changed.