Method 1 : You can add an operation after the frame driver. There are two methods to do it : Either tweak the driver (lesser solution) or add a math node afterwards (preferred solution, at least if you aren't really at ease with drivers). Say you would want the value to increase more slowly. To remove the driver, right click in the field and choose : Delete Driver. The field becomes purple to indicate it's now driven. This driver will have the same value as the current frame. This will automatically create a driver (which can get a bit complicated if you want to go into the details, but in this case there is no need).

Left-Click in the value field like you would do if you wanted to input a new value, and type #frame.

Say you have this kind of setup and would like the Value node to output the frame number. Although, like in the shader editor where this information is also sometimes needed, you can use a very simple driver to access the frame number directly. I don't think there will be a node specifically designed to access the frame number.

Bb flashback show frame number