Hello.
I've detected two problems.

First
If I execute...:

void setup() {  Serial.begin(9600); }
void loop() {  Serial.println(2);  }

...value 2 is shown at the top of Serial Plotter but Y-axis doesn't show the numerical coordinates. If I put a greater value (like 10, for instance), then it's fine.

Second
If I execute...

void setup() {  Serial.begin(9600); }
void loop() {  Serial.println(random(55));  }

...graph is shown fine, but if I add a delay after Serial.println() (only if delay time is more than 700ms aprox.!!) , the Y-axis boundaries are not updated accordingly, showing always from 0 to 400 values (and not from 0 to 60 or similar, as expected).

Thanks