Len(data.trn_ds) seems to produce an incorrect number

While playing around with lesson 2 and 3 data I noticed that when I run len(data.trn_ds) I get a different number than when I run !ls {PATH}train | wc -l. Running len(data.trn_ds) produces a number which does not change, no matter what the actual count of files in that folder is.

Has anybody else noticed the same thing?