As a rule , doors are glazed (installed) from the inside and windows from the outside

   'Tight' size refers to the dimensions of the aperture into which the gloss is to be fitted.

  To ensure a good fit, glass size is generally 3 to 4mm less overall than tight size

   Extra care should be taken with old unsquare frames.

   If possible remove the putty or bead so that sizes can be checked.

   I need t know the visible size if your panel is to have a border.