Simple Excel Data Validation didn't accept typed numbers -

I am working with Excel 2013

I would like to make a custom data validation on cell A7

or

• Any number of lengths of 6
• >

< P> I know that the formula below is not optimized but it is only for test combination or purpose, whereas the formula given below by the data validation window is accepted, while testing, no number is accepted Is done.

  = OR (and (ISNUMBER (A7); LN (A7) = 3); and (ISNUMBER (A7); LN (A7) = 6))  

The same formula (re-formatted for easy readings):

  = or (and (ISNUMBER (A7); LN (A7) = 3); And (ISNUMBER (A7); LN (A7) = 6))  

Any ideas why this formula has not typed numbers

thanks

This error will occur when formatted on A7 on text Has been done: