I'm using version 1.7.9 and I found out that you must only use whole numbers. Don't use decimals. Another thing is round the numbers to the nearest 10th if the number for the x coordinate was for example -88.58690 use -89. Or just look at the number in (parentheses) That one tells you the rounded up number. The reason for this is because if you were to spawn a player inside a (tube) with a pressure plate below, make sure for one, that the y coordinate is a block above the pressure plate and that the x or z coordinate is rounded if needed otherwise it'll teleport them inside the blocks of the tube which wont work and so it'll just spawn you at the world spawn instead of at those coordinates.
Mark Gontar
I'm using version 1.7.9 and I found out that you must only use whole numbers. Don't use decimals. Another thing is round the numbers to the nearest 10th if the number for the x coordinate was for example -88.58690 use -89. Or just look at the number in (parentheses) That one tells you the rounded up number. The reason for this is because if you were to spawn a player inside a (tube) with a pressure plate below, make sure for one, that the y coordinate is a block above the pressure plate and that the x or z coordinate is rounded if needed otherwise it'll teleport them inside the blocks of the tube which wont work and so it'll just spawn you at the world spawn instead of at those coordinates.