Hhmm, let's see. That's a broad question. Here's my stab at answering.
For signing free agents, the most important figure is "projected budget room". In its simplest form, projected budget room = your budget minus your current payrolls for players and personnel. In actuality it is slightly more complicated. It is your budget minus your total expected expense for the year for players and personnel minus any outstanding offers already made. You can't see your total expected expense for the year anywhere, but you can see your expense for year-to-date for players and personnel. Your expenses YTD include salaries already paid out (which is based on number of games played) plus any salaries for the rest of the year and following years that were paid off when players or personnel were released/fired). You CAN calculate the projected budget amount accurately only if you diligently track your actuals outside of the game. It works 99.9% of the time and takes a lot of understanding. Unless you want to spend a LOT of time tracking, then trust the games calculation of projected budget amount.
I should further say that the "player payroll amount" on the front office page does not always agree with the "player salary report". If you have any players with a minor league contract, it says that on the player salary report. But if at any time you have one or more such players on your 25-man (active) roster, then the "player payroll" under general information includes the minimum major league salary for each such player. In the off-season and especially in pre-season, you can have players with minor league contracts on your active roster. When Opening Day arrives, they will automatically start drawing the minimum major league salary if you have not returned them to the minors prior to opening day.
"available for player or staff signings" under "Owner Comments" is projected budget room plus cash but not more than the league salary cap. The description fails to say "but not more than the salary cap", but it IS part of the calculation of the amount available.
How did your budget get calculated? It = prior year gate revenue plus prior year playoff revenue plus prior year merchandising revenue plus current year media contract.
Hire a CFO