Hi Adnan,
Sure, there should be at least 2 ways of doing this, probably more.
For the slot that you are trying to collect, you can create it as a "Regular Expression" Type Slot, and just define a regular expression on it that validates 8 digits (For example: ^\d{8}$ ).
If the information provided by the customer doesn't match the Regex, then it will be treated as "No Match" (which you can then set the Bot Flow to repeat X times on No Match, etc.)
Also, another way of doing this, is using the "Custom Validation" property on the "Ask for Slot" component. In there you can set any expression to validate as a boolean (true or false), after the collection is done. So for instance, you could just use the "Length()" expression to check if your slot variable has 8 digits of length.
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Marcello Jabur
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