One, the 155 planning divisor is the companies (company's) for planning the numbers of pilots they should have.
It's not what they should have, it's the minimum number of pilots they
need. When the divisor goes up, that same number of pilots just work harder. In the early days or in the event of a downturn when the pilots are actually doing less than 155, matching the number of pilots to that divisor determines the maximum number they need to pay, even if they aren't achieving those hours.
To put it another way. How many pilots do we need to do a 155 hour divisor with the planned flying? If the flying increases the pilots just work harder.