terraform - how do you override a default variable from module

How to overwrite base module variable in extended module ? Here I want to change transition_to_std_ia_day to override the value to 120 days, how do I do that? when I try to access the variable to set the variable , terraform plan complains "An argument or block definition is required here" !!

base module main.tf:

resource "aws_s3_bucket_lifecycle_configuration" "bucket_lifecycle_config" {
  bucket = module.s3.bucket_name
  
  rule {
    id     = "lc_pd_rule"
    status = "Enabled"

    "transition" {
      
      content {
        days          = var.custom_lc_rule.transition_to_std_ia_day
        storage_class = "STANDARD_IA"
      }
    }

variable "custom_lc_rule" {
  type        = map(string)
  description = "Custom lifecycle rule to choose days for Standard-IA, Glacier, and Expiration."
  default = {
    "transition_to_std_ia_day" = "30",
    "transition_to_glacier_day"     = "90",
    "objects_expire_days"            = "365"
  }
}

-- here is my sub module life-cycle config calling source as base module above.

resource "aws_s3_bucket_lifecycle_configuration" "bucket_lifecycle_config" {
  bucket = module.s3.bucket_name
  rule {
    id     = "prod_rule"
    status = "Enabled"

      transition {
        days          = var.custom_lc_rule.trans_standard_ia_day
        storage_class = "STANDARD_IA"
      }
      
      transition {
        days          = var.custom_lc_rule.trans_glacier_day
        storage_class = "GLACIER"
      }
    
     expiration {
        days = var.custom_lc_rule.expiration_day
        
    }
  }
}

variables.tf - submodule variables tf file has the transition and expiration days defined as below.

variable "custom_lc_rule" {
  type        = map(string)
  description = "Custom prod lifecycle rule for Standard-IA, Glacier, and expiration days."
  default = {
    "trans_standard_ia_day" = "60",
    "trans_glacier_day"     = "180",
    "expiration_day"            = "2555"
  }
}

Wondering how the tf runtime reads these variables? I see very random behavior. code works fine sometimes. but weird sometimes it doesn't consider submodule variables .