The phrase "a predefined amount of" is correct and usable in written English.
You can use it when referring to a specific quantity that has been established in advance, often in contexts like finance, programming, or project management.
Example: "The budget for the project includes a predefined amount of resources allocated for marketing."
Alternatives: "a set quantity of" or "a specified amount of".
The biodegradability of any substrate is determined by feeding the known amount of substrate to a predefined amount of sludge.
If the camera does not respond within a predefined amount of time, it is considered to be out of service and should be retrieved for inspection.
Farrel (1957) defined the enterprise efficiency as generating an amount of output that was sufficiently more than a predefined amount of input.
To avoid queue overflow, each head node has a predefined amount of jobs that can be queued.
We implemented an appropriate memory allocator and manager that allows PEAR to use only a predefined amount of memory that the user can specify via a command-line switch.
In the case of Time Trade-Off (TTO), the respondent is invited to express his/her willingness to give up part of a predefined amount of lifetime (with a maximum of 10 years) in order to avoid the presented (suboptimal) health state.
Each of these qualifying races has a different, predefined amount of slots that can be won.
The existing DLCS requires constant operator intervention, e.g., whenever the load is about to exceed a predefined amount, it needs operator's intervention to control the on/off status of the load.
During each iteration, each user increases his transmission rate by a predefined amount.
The dimension of the original data can be reduced by retaining only a small number of principal components that describe the predefined amount of variability.
After that, cupric ions were reduced to metallic copper or copper oxide nanoparticles by adding the predefined amount of reducing agent sodium borohydride (0.5 mol/L).
