Tested the issue in Android and able to reproduce the issue. Similar behavior is observed since Chrome M-61.

Steps Followed:
1. Launched the Chrome Browser.
2. Reset History and Data Saver - RESET STATISTICS 
3. Browse couple of sites.
4. Navigate to Data Saver page from Chrome settings.
5. In the Data Saver page observe that there is rounding off difference between Data Saved, Data Used and sum of Data Usage breakdown. 

Chrome versions tested:
61.0.3142.0, 64.0.3282.137(Stable), 66.0.3336.4(Canary)

(In the M-60 and earlier builds, data break down is not displayed and couldn't verify sum on those builds)

OS:
Android 7.0.0

Android Devices:
SM-J701F, Build/NRD90M

This seems to be a Non-Regression issue as same behavior is seen since M61. Hence removing the ‘Needs-Bisect’ label. Untriaged for further input's on this issue.

Please navigate to below link for log's and video--
go/chrome-androidlogs/808201

Thanks!

Basic complaint here is that breakdown counts do not sum to same value as displayed total. Looks like more than just rounding issue - are we not sampling counts consistently for total and breakdown?

IIRC, the total is stored in a pref while the breakdown comes from a DB, the former for performance. They are written at the same time and *should* agree. I can think of a few ways to fix this:

1) compute the total from the breakdown, but that means more (maybe too much) processing on the main settings page. 
2) move the total to the DB, so that writes happen to the same place.
3) make one the authoritative source, and adjust the "other" bucket to agree.  

I prefer them in that order.

Repro-ed this for inconsistency with Data Used - beyond rounding error. 
Interestingly, Data Saved may be just rounding issue. So perhaps we need to first focus on where breakdown is not getting updated when total is.

Summarizing data from screenshot: 
  - Total Data Used 4.35MB != 2.21MB + 1.21MB + 311KB + 57.41KB
  - Total Data Saved 744KB ~= 684KB + 51.61KB + 7.16KB + 319B

Deleted: saveddatabreakdown.png 150 KB

	saveddatabreakdown.png 150 KB View Download

CC-ing Raj in case he might have insight as to where Used count is counted without breakdown counted.

DataReductionProxyNetworkDelegate::CalculateAndRecordDataUsage() only record total and it does have the URL so that looks like a big hole that should be straightforward to fix.

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Raj, with your data use ascription refactoring landed, do you expect this issue is now resolved? 

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This is fixed when network-service is enabled.