This is not a simple calculator, it is designed for calculations when creating new missions for GTA 1. A very useful thing. Written in 1998 in VisualBasic, which is now almost never used.

Health setting:
The utility may not start if you do not have "MSVBVM50.DLL" on your PC. This computer system file may not be installed on many modern PCs, but it just allows you to run utilities written in VisualBasic.
Simply downloading msvbvm50.dll is not enough; it must be placed in one of the folders in the Windows directory. This is the System32 folder for a 32-bit copy of Windows or the SysWOW64 directory for a 64-bit version. It is necessary not only to put the library in place, but also to register it in the registry. After this, the program will start without error.
Inside the archive there is a program called MSVBVM50.exe that does all this work for you.

Installation:

Unpack the contents.
Open MSVBVM50.exe and click on "ok", the program must be in the same folder as MSVBVM50.DLL so that it sees MSVBVM50.DLL and installs it in the registry.