Jetpack compose. Visual transformation getting incorrect offset

Question

I'm using composable BasicTextField:

BasicTextField(
   value = viewModel.state.phone,
   onValueChange = { 
       viewModel.onPhoneChanged(if (!it.startsWith("+")) "+$it" else it)
     },
   visualTransformation = PhoneNumberTransformation(),
)

My viewModel:

fun onPhoneChanged(phone: String) {
   state.update {
       it.copy(phone = phone)
   }
}

As you can see, if the user enters a number as the first character, I force a plus to be added to the zero position.

The plus is added, however in the visual transformation I get an offset equal to 1. For example, I enter 9, in which case +9 should be displayed in the text field, in the visual transformation in the originalToTransformed the offset is equal to 1, although the offset should already be equal to 2 (we must take into account plus). What could be the problem ? help me please