You can go to Model Explorer > find 'gate_h' and select it > go to the general settings of the variable > force change the size to [1 20].
Also found a similar MATLAB Answers post explaining the same - https://www.mathworks.com/matlabcentral/answers/17891-inferred-size-1-13-for-data-32-does-not-match-back-propagated-size-13-from-simu
Thanks!
