A custom validation list may includes one or multiple rules.
First, you need choose the rule you'd like to add from rules list.
Different rule has different settings, you need to set right value for the settings.
For example, you'd like to limit phone number only numbers and the first number is not 0 or 1 then you may add the following rules.
1). Limit the phone number length to 10
2). Limit the input value must be numeric characters, as the first number cannot be 0 or 1 so set it between 2000000000 and 9999999999
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