How is the Baron Power Play calculated?

In the MSI Game G2 vs FW Caps managed to steal Nash.
The Baron Power Play total was +5431g. How was this calculated?
I could imagine it to only count turrents and kills, but it seems to add / substract gold on the fly.
What influences this counter?

This is just the total change in gold while Baron (Nash) buff was active.

A Baron Power Play of +5431g means that for the 3.5 minutes that G2 had the Hand of Baron buff, they earned 5431 more gold than FW in that time frame.

If the buff ends early, then the Baron Power Play ends there. Note that it's also possible for a Baron Power Play to be negative: if 4 members lose it and the opposing team proceeds to take several objectives before killing the last member, the opposing team would have come out ahead, and so the power play would have negative value. Of course, in this case, the production staff would probably not display the graphic :-)

I found a comment by Riot SwampWTFox, an Associate Producer for the NA LCS, that confirms this:

It's the difference in gold a team gained or lost whilst having the baron buff. So for example; if Team A gets baron and the earns 4,000 gold, and during that time, Team B earns 2,000 gold, then the Baron Power Play will be +2,000 gold. On the other hand, if Team A gets baron, but then is immediately aced by the enemy team, and lose multiple turrets, you might very well have a Baron Power Play of negative value.