@CarlosLuis Nice graph!! So in the screenshot, you took 2.5 U at around 5 PM, and at 6:15 PM, about an hour later, you used up about 50% of that bolus, with 1.28 U IOB. Does that seem right?
Here is another conversation on FUD discussing Tandem IOB and gives a nice graph of the IOB absorption time. It shows insulin is absorbed over a 5+ hour period, with 50% absorbed only after 3+ hours, with about 20% of the insulin used in the first hour. Maybe the Tandem algorithm in considering bolus, together with other criteria as well, in their IOB calculus? Your basal was reduced during this same hour, so that could play a role as well? If you used 20% of your bolus (typical for insulin absorption shown on the other FUD conversation graph) during this hour, you should have about 2.0 U IOB. Maybe the Tandem subtracts the basal that you did not receive (from your programmed 1.1U) due to the algorithm reducing the basal? So that your IOB is 2.0 U minus basal amount you did not receive (eg., 0.7U)?
@beans_betes Do you have the T:Connect Mobile app? It looks very useful!