Update README.md

Author: excavator-matt

README.md

@@ -448,7 +448,7 @@ No modules.
 | <a name="input_enable_dns_support"></a> [enable\_dns\_support](#input\_enable\_dns\_support) | Should be true to enable DNS support in the VPC | `bool` | `true` | no |
 | <a name="input_enable_flow_log"></a> [enable\_flow\_log](#input\_enable\_flow\_log) | Whether or not to enable VPC Flow Logs | `bool` | `false` | no |
 | <a name="input_enable_ipv6"></a> [enable\_ipv6](#input\_enable\_ipv6) | Requests an Amazon-provided IPv6 CIDR block with a /56 prefix length for the VPC. You cannot specify the range of IP addresses, or the size of the CIDR block | `bool` | `false` | no |
-| <a name="input_enable_nat_gateway"></a> [enable\_nat\_gateway](#input\_enable\_nat\_gateway) | Should be true if you want to provision NAT Gateways for each of your private networks | `bool` | `false` | no |
+| <a name="input_enable_nat_gateway"></a> [enable\_nat\_gateway](#input\_enable\_nat\_gateway) | Should be true if you want to provision NAT Gateways for your private networks. Unless `single_nat_gateway` or `one_nat_gateway_per_az` is set, it will create one NAT Gateway per private subnet | `bool` | `false` | no |
 | <a name="input_enable_network_address_usage_metrics"></a> [enable\_network\_address\_usage\_metrics](#input\_enable\_network\_address\_usage\_metrics) | Determines whether network address usage metrics are enabled for the VPC | `bool` | `null` | no |
 | <a name="input_enable_public_redshift"></a> [enable\_public\_redshift](#input\_enable\_public\_redshift) | Controls if redshift should have public routing table | `bool` | `false` | no |
 | <a name="input_enable_vpn_gateway"></a> [enable\_vpn\_gateway](#input\_enable\_vpn\_gateway) | Should be true if you want to create a new VPN Gateway resource and attach it to the VPC | `bool` | `false` | no |
@@ -581,7 +581,7 @@ No modules.
 | <a name="input_redshift_subnets"></a> [redshift\_subnets](#input\_redshift\_subnets) | A list of redshift subnets inside the VPC | `list(string)` | `[]` | no |
 | <a name="input_reuse_nat_ips"></a> [reuse\_nat\_ips](#input\_reuse\_nat\_ips) | Should be true if you don't want EIPs to be created for your NAT Gateways and will instead pass them in via the 'external\_nat\_ip\_ids' variable | `bool` | `false` | no |
 | <a name="input_secondary_cidr_blocks"></a> [secondary\_cidr\_blocks](#input\_secondary\_cidr\_blocks) | List of secondary CIDR blocks to associate with the VPC to extend the IP Address pool | `list(string)` | `[]` | no |
-| <a name="input_single_nat_gateway"></a> [single\_nat\_gateway](#input\_single\_nat\_gateway) | Should be true if you want to provision a single shared NAT Gateway across all of your private networks | `bool` | `false` | no |
+| <a name="input_single_nat_gateway"></a> [single\_nat\_gateway](#input\_single\_nat\_gateway) | Should be true if you want to provision a single shared NAT Gateway across all of your private networks. Setting this to true overrides `enable_nat_gateway` | `bool` | `false` | no |
 | <a name="input_tags"></a> [tags](#input\_tags) | A map of tags to add to all resources | `map(string)` | `{}` | no |
 | <a name="input_use_ipam_pool"></a> [use\_ipam\_pool](#input\_use\_ipam\_pool) | Determines whether IPAM pool is used for CIDR allocation | `bool` | `false` | no |
 | <a name="input_vpc_block_public_access_exclusions"></a> [vpc\_block\_public\_access\_exclusions](#input\_vpc\_block\_public\_access\_exclusions) | A map of VPC block public access exclusions | `map(any)` | `{}` | no |