To suppress the byte-compiler warning, try adding this before your code, starting in column 0 (leftmost):

 (declare-function increase-count "your-file-name.el")


`C-h f declare-function` tells you:

> **`declare-function`** is a Lisp macro in `subr.el`.

> `(declare-function FN FILE &optional ARGLIST FILEONLY)`

> Tell the byte-compiler that function `FN` is defined, in `FILE`.
The `FILE` argument is not used by the byte-compiler, but by the
`check-declare` package, which checks that FILE contains a
definition for `FN`.

> `FILE` can be either a Lisp file (in which case the `".el"`
extension is optional), or a C file. C files are expanded
relative to the Emacs `"src/"` directory. Lisp files are
searched for using `locate-library`, and if that fails they are
expanded relative to the location of the file containing the
declaration. A `FILE` with an `"ext:"` prefix is an external file.
`check-declare` will check such files if they are found, and skip
them without error if they are not.

> Optional `ARGLIST` specifies `FN`’s arguments, or is `t` to not specify
`FN`’s arguments. An omitted `ARGLIST` defaults to `t`, not `nil`: a `nil`
`ARGLIST` specifies an empty argument list, and an explicit `t`
`ARGLIST` is a placeholder that allows supplying a later arg.

> Optional `FILEONLY` non-`nil` means that `check-declare` will check
only that `FILE` exists, not that it defines `FN`. This is intended
for function definitions that `check-declare` does not recognize,
e.g., `defstruct`.

> Note that for the purposes of `check-declare`, this statement
must be the first non-whitespace on a line.

> For more information, see Info node [**`(elisp)Declaring Functions`**](https://www.gnu.org/software/emacs/manual/html_node/elisp/Declaring-Functions.html).