+1Given that the term "απόλυτες διαστάσεις" is commonly used in architecture to refer to absolute dimensions (in contrast to relative dimensions), it might be a safer bet to use something more descriptive
Less sternly, yet still firmly put:Απαγορεύεται οποιαδήποτε απόκλιση από τις διαστάσεις
Albeit a bit stern, at least it's clearer.