One block, two very different tasks
Sprachbausteine is grammar and lexis in gap form; Leseverstehen is matching and multiple choice on texts. They reward opposite instincts — one wants you to slow down and inspect a sentence, the other wants you to move. Candidates who do not decide in advance how to split the block tend to overspend on the grammar gaps and then rush the reading, which is the expensive way round because reading carries the larger share of the points.
The reading half itself is three parts built from matching and multiple choice, and its share of the total exam mark is published by telc and printed on this page with its source. There is no official per-part timing, so any schedule you find online is somebody’s recommendation, not a rule.