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Sure, and browses which rejects or periodically delete cookies will be counted multiple timesActually no, they will be counted only once towards the period in which we are counting them (daily or monthly) as long as the IP of the device is the same. Not multiple times. In mobile IPs are shared due to NAT-ing and thus, this method undercounts.
>a device might use multiple browsers (especially the embedded browsers on mobile devices)
This is correct, multiple browsers on one device will be counted multiple times. This is less of a common browsing pattern than using the same method of access every time.