The phrase appears to be a specific citation or file reference, likely referring to the paper "The Dropbox Design" or a related technical study .
If you are reading this in a systems paper, it usually pertains to: : Sending only changed bits of a file. Dropbox (32) ts
: Distributed systems and cloud storage architecture. The phrase appears to be a specific citation
: May refer to a 32-bit timestamp or a specific Thread State in system debugging. Dropbox (32) ts
If you are looking for a to a specific research PDF.