I have tried many times to register (pre registration) in Journal of Number Theory of Elsevier publisher, when I put my Personal Keywords I got the below attached error notice, I separated my keywords by semicolons then by comma, however they asked for 5 keywords, I plugged the required keywords but always the same notice error:
"You did not enter the required number of Keywords".
"Please use the button below to go back to the Previous Page and enter the missing information":
I checked the Author guide for pre registration but unfortunately no talking about that personal keywords: