I think it's trying to compare what it measures to some other value, but that other value is not consistent in any way, so what it measured was 20x bigger... I don't know what that other value is, but looking at the YAmon page it looks like it's supposed to be numbers from your ISP?
I have no idea how it works, but maybe there's some way it can check your modem stats if you give it a particular URL to retrieve or something? It looks like that's the purpose of this particular data. I think you can safely ignore it.
I've made some pretty major changes going from YAMon v3 to v4. To date, I've been focussed on the router side of things (and changed jobs at the beginning of the month). This could (hopefuylly) be a simple reporting issue.