Why is my signal not updating the UI when using `++` or `--` operation

I have this scenario, where I want to increment/decrement two values, so I use the standard ++ and -- operation to do this inside the update method of signals.

import { Component, signal } from '@angular/core';
import { bootstrapApplication } from '@angular/platform-browser';

@Component({
selector: 'app-root',
template: `
<hr/>
{{id()}}
<hr/>
{{num()}}
`,
})
export class App {
id = signal(1);
num = signal(1000);

ngOnInit() {
setInterval(() => {
this.id.update((prev: number) => prev++);
this.num.update((prev: number) => prev--);
}, 2000);
}
}
bootstrapApplication(App);


Why are my signals updated, when I clearly incremented them.

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