Another FLex Situation

[JefferMC]

Help me with this situation. Monday I was the scorekeeper (coach/umpire/Dad/scorekeeper, the list of hats keeps growing) for the home team. Both teams using DP/Flex. Neither really had them marked on the line up card with the proper terms, but that's okay. Home team coach intends to substitute player in at the top of the 4th inning, intending that she takes over offensive duties for the DP (in the #9 slot) and 3rd base for Flex (in the #10) position. I'm thinking that the DP/Flex disappears into a regular player in slot 9.

I know the player must go into the #9 slot in the batting order. But what do I do with the Flex slot? If giving opinions regarding the scorebook is beneath you, what would you do on your lineup card?