When iPWMinder downloads files from Dropbox, it stores (caches), the files and some meta-data on your device. This helps to limit the data usage needed and allows you to access your password repository files, while offline.
To clear the cached Dropbox files, tap on the Dropbox Integration icon, on the Welcome Screen:
On the Dropbox Integration screen, you can see the current size of the Dropbox cache:
To clear the cache, tap on the Clear Cache button:
After confirming, the cached files are deleted: