Easy one, it just means the last update run only did Primegrid for you which was 106.
Last update on a project is the last update when that project last updated. I don;t reset the field every time for all projects .
So say, on a certain run of the stats it notices that WCG, PrimeGrid updated and you had done 1000 and 2000 respectively, you would see 1000 in the last update column for WCG, 2000 in the last update column for PrimeGrid and 3000 in the last update combined.
Then say next run, perhaps 45 mins later it sees that Yoyo and Einstein had updated and you had done 4000 and 5000 respectively, you would then see -
WCG - 1000
PrimeGrid - 2000
Yoyo - 4000
Einstein - 5000
Combined - 9000 - sum of the Yoyo and Einstein last updates as they were what ran in the last update.
I have considered in the past marking the projects that ran in the last update somehow on screen as this has been asked before.
Does that make sense ?