The $2,700 recharacterized from Roth to TIRA is not part of your Roth contribution basis. The recharacterized amount is treated as having been originally contributed to the TIRA.
You question is confusing because the recharacterized amount ended up not being part of your Roth IRA contribution basis in the first place. It's not clear whether you've included the $2,700 in the starting figure to begin with. (It should not have been.) Net contributions to the Roth IRA would be the sum of your Roth IRA contributions that remained Roth IRA contributions prior to 2018 (so, not including the $2,700 in question) minus any regular distributions from the Roth IRA prior to 2018.
