In Practical Programming for Strength Training percentages are used just to illustrate what the approximate intensity of the lift should be. They are not used to tell a lifter to determine what weight should go on the bar. The best source of data to use to determine your intensity day weights would be to base them off of recent, established 5RMs.
If you do not have established 5RMs there is a good chance that you are still a novice and the Texas Method is not the right program for you.