Last 30 to 10 minutes of the day way more costs are getting posted

Hi team,

our Taboola Account is set on Europe/Berlin time. We have get over the day all 30 mins the costs posted into RedTrack via the API, but in the last 30-10 minutes of the day exorbitant more costs are getting posted. Is this because the bidding strategy is trying to spend the remaining budget or is this because some costs are not getting posted during the regular 30 minute period during the day but (only) at the end of the day?

My question is basically, how come my ROAS is decreasing by 40% in the last 30-10 minutes of the day?

Best,

Martina