That’s not going to help you I’m afraid.
Every value since the reset needs to be increased by the value of the feed immediately prior to the reset. 19days at 10s intervals for 3 feeds is nearly half a million datapoints that need editing, that’s why you need a script/tool.
In the interests of damage limitation, you could create a duplicate set of new feeds and start collecting data asap, if you fix the old feeds you can delete the new ones, if you can’t fix the old ones you have the new ones with at least a little history if/when you decide to give up on the old ones. You can just name them “import_kwh2” etc for now and rename later. Position each new feed immediately after the old feeds in the input processing lists.
This sounds a bit drastic I know, but you previously said you would delete all data prior to the reset, so it’s only an additional 19 days data at risk.
Thinking about it, there is a new feature in the pipeline to “trim” phpfina feeds to clear data older than a certain point. That is in the master branch of emoncms I believe, I have not tried it and the emonPi/SD runs the stable branch not master by default, you might want to explore switching branches and trying that feature, but again, I’m not familiar with the feature and I do not know how confident you are to manually switch branches and more importantly, deal with any “hiccups” that may pop up, it may well be straightforward and go without any “hiccups” at all, but I’m not in a position to reassure you that would definitely be the case.