Although 6*(900/Tempo/Speed), in my case, comes out to 7.2.
900/((6*Tempo)/Speed) works, however.
Oh yes, the latter is correct.
About that comment: The first echo channel is played about 0.72 second later than the main channel, and the second echo is even more delayed. I understand that you might be following the original song, but some parts are very strange because of the echo, e.g. frame 07 rows 30 and 34 where a G, an A and a B is nearly played at the same time.
I suggest lowering the volumes of the echos for increasing the volume of SQ1.