First. Don't worry. The triangle symbol means the download mode was interrupted.
Next. Charge the tab. Plug it in and let it sit for a day. The tab needs to be fully charged.
Second. Make absolutely sure you have the right cm version for your tab. The wrong version will make the tab into a brick.
Read the instructions on how to flash that rom. Then read it again.
Sometimes, odin does not detect tab. Just try different combinations of turning it on and plugging it in. Reflash.
Hope this helps.
Sent from the Galaxasaurous tabalonicus Rex
Sent from a Galaxus tabosaurous REX from 40m below.