Just wow! I’m amazed… that looks like over 500amp hrs of lithium I think
The 50w is a user setting, so when 50w of export is seen, and assuming it’s not rising or falling rapidly (as export will do briefly when a load is switched on/off) proportional diversion to the resistive load will occur - export limiting or diversion isnt instantly responsive, so an amount of import/export will be seen as loads turn on/off.
I suspect my battery is around 750Ah.