Instead of using anchors, I would create a mask using event Pan/Crop mode which you can find here. Event Pan/Crop is the middle button that's at the end of any video/text clip.
Once you're in this mode, make sure you've checked the mask box since it's not enabled by default. Once it's enabled, select the Rectangle or Square Mask Creation tool which you can find on the left side of the tab.
Once you've selected that, you can create a rectangle over the text that you want to be hidden at first. Once you have the mask where you want it to be make sure that the mask's mode is Negative. This mode will make anything inside the mask disappear. You can change the mode of the mask under the Paths tab which is right next to where the mask creation tools are.
After you've set your mask to negative all you have to do is animate the mask via keyframes.