I recently configured an automation on ios shortcuts for my Baby Tracker app that basically send the input, in that case the number of mL fed to a sensor on my HA server.
The issue I’m having is that if I input two times in a row 80mL for an example, it will only display one state input in HA instead of two.
That’s the way Home Assistant handles identical successive values for all entities. If the latest received value is identical to the previous one, nothing happens. Basically, the latest identical value is ignored (which is the behavior you have observed).
The only workaround for your application is to avoid 80 → 80 → 80 so make the second feeding 81 ml (anything other than 80) to get 80 → 81 → 80.
EDIT
I overlooked to say, congratulations for the latest addition to your family!
What you said made me realized that the date/time is never the same value, so I tried setting the date/time as the value and the amount as an attribute, it works well like this!
For future reference, the custom is to assign the Solution tag to the first post that resolves the problem or answers the question (and optionally explains the root cause of the problem), not the post that implements the solution.
In this case, the solution is to ensure successive values are not identical. Whether you achieve it by changing the feeding amount or by using an entirely different value (the time of feeding) either method implements the solution to avoid successive identical values.